- Email: [email protected]
hyperactivity disorder
ORIGINAL ARTICLES
A randomized, double-blind, placebo-controlled trial of docosahexaenoic acid supplementation in children with attention-deficit/hyperactivity disorder Robert G. Voigt, MD, Antolin M. Llorente, PhD, Craig L. Jensen, MD, J. Kennard Fraley, MPH, Marcia C. Berretta, LMSW, and William C. Heird, MD Objective: To determine whether docosahexaenoic acid (DHA) supplementation for 4 months decreases the symptoms of attention-deficit/hyperactivity disorder (ADHD). Study design: Sixty-three 6- to-12-year-old children with ADHD, all receiving effective maintenance therapy with stimulant medication, were assigned randomly, in a double-blind fashion, to receive DHA supplementation (345 mg/d) or placebo for 4 months. Outcome variables included plasma phospholipid fatty acid patterns, scores on laboratory measures of inattention and impulsivity (Test of Variables of Attention, Children’s Color Trails test) while not taking stimulant medication, and scores on parental behavioral rating scales (Child Behavior Checklist, Conners’ Rating Scale). Differences between groups after 4 months of DHA supplementation or placebo administration were determined by analysis of variance, controlling for age, baseline value of each outcome variable, ethnicity, and ADHD subtype. Results: Plasma phospholipid DHA content of the DHA-supplemented group was 2.6-fold higher at the end of the study than that of the placebo group (4.85 ± 1.35 vs 1.86 ± 0.87 mol % of total fatty acids; P < .001). Despite this, there was no statistically significant improvement in any objective or subjective measure of ADHD symptoms. Conclusion: A 4-month period of DHA supplementation (345 mg/d) does not decrease symptoms of ADHD. (J Pediatr 2001;139:189-96) From the Division of Developmental and Behavioral Pediatrics, Mayo Clinic, Rochester, Minnesota; Departments of Pediatrics, Psychiatry, and the US Department of Agriculture, Agricultural Research Service Children’s Nutrition Research Center, Baylor College of Medicine, Houston, Texas.
This work is a publication of the US Department of Agriculture, Agricultural Research Service (USDA/ARS) Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, and has been funded in part with federal funds from the US Department of Agriculture, Agricultural Research Service, under Cooperative Agreement No. 386250-1-003. The contents of this publication do not necessarily reflect the views or policies of the US Department of Agriculture, nor does the mention of trade names, commercial products, or organizations imply endorsement by the United States Government. This study was also funded in part by a grant from the Martek Biosciences Corporation, Columbia, Maryland, which, in addition, provided the docosahexaenoic acid (DHA) and placebo capsules used in the study. Submitted for publication Nov 7, 2000; revision received Feb 1, 2001; accepted Mar 23, 2001. Reprint requests: Robert G. Voigt, MD, Division of Developmental and Behavioral Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, 200 First St SW, Baldwin 3A, Rochester, MN 55905. 9/21/116050 doi:10.1067/mpd.2001.116050
Attention-deficit/hyperactivity disorder (ADHD),1 characterized by developmentally inappropriate and disabling levels of inattention, impulsivity, and/or hyperactivity, is one of
See editorial, p 173. the most common chronic health conditions affecting school-aged children.2,3 Although 70% to 90% of children with ADHD respond positively to treatment with stimulant medications (eg, methylphenidate and dexADHD
Attention-deficit/hyperactivity disorder CBCL Child Behavior Checklist DHA Docosahexaenoic acid DSM-IV Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition TOVA Test of Variables of Attention
troamphetamine sulfate),3,4 there is considerable concern regarding potential adverse consequences of protracted use of these medications,5-10 particularly because data showing that stimulant medication improves the long-term prognosis of children with ADHD are scarce.11-15 Therefore, alternative treatments for ADHD are widely used.16 Currently, there is considerable interest in the possibility that dietary supplementation with the long-chain, polyunsaturated fatty acid, docosahexaenoic acid (DHA [22:6ω3]), will decrease the symptoms of ADHD. DHA is present in large amounts in 189
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the structural lipids of brain cell membranes, including those of the synaptic terminals,17-21 and children with ADHD have been shown to have low plasma and erythrocyte phospholipid levels of DHA.22,23 Assuming that brain levels also are low, it has been argued that DHA supplementation will increase levels and that the resulting alterations in synaptic transmission will decrease the symptoms of ADHD. Indeed, despite a lack of data to support either efficacy or safety, DHA supplements are readily available and are being marketed for the treatment of children with ADHD.16 The objective of this study was to determine the efficacy of DHA supplementation in reducing symptoms of ADHD.
medication, underwent a confirmatory diagnostic interview with a neurodevelopmental pediatrician to confirm responses to the telephone interview and to ensure that each met strict Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)1 criteria for ADHD and had clear historical evidence of clinically significant impairment in social or academic functioning. Children who met DSM-IV criteria for oppositional defiant disorder or conduct disorder, both of which are common comorbid conditions in children with ADHD,24 were not excluded. Seventy of the 90 potential subjects who completed the diagnostic interview were considered to have idiopathic ADHD and were offered study enrollment; 63 returned for randomization.
METHODS
Randomization
Subjects Parents or guardians of 250 children who responded to advertisements for study volunteers were screened by telephone. A total of 160 children were excluded for one or more of the following reasons: (1) ineffective treatment with stimulant medication; (2) treatment with other psychotropic medications; (3) previous diagnosis of other childhood psychiatric disorders (ie, anxiety, mood, thought, or bipolar disorders), (4) use of dietary supplements other than vitamins, (5) occurrence of a significant life event (eg, death of an immediate family member, parental separation or divorce, or relocation) within 6 months; (6) a history of head injury or seizures; (7) receipt of special education services for mental retardation or a pervasive developmental disorder; (8) premature birth; (9) exposure to tobacco, alcohol, or other drugs in utero; and/or (10) diagnosis of a disorder of lipid metabolism or other chronic medical condition. The remaining 90 children, all of whom had previously been given a diagnosis of ADHD by a physician and were being treated successfully with stimulant 190
All subjects were randomly assigned in a double-blind fashion according to a computer-generated randomization scheme to receive either an algae-derived triglyceride capsule (DHASCO; Martek Biosciences Corporation, Columbia, Md), providing 345 mg of DHA per day (n = 32), or a placebo capsule (n = 31) for 4 months. Both capsules were provided by Martek Biosciences Corporation and were identical in appearance. They were dispensed by the Investigational Pharmacy of Texas Children’s Hospital according to the computer-generated randomization scheme. The number of capsules dispensed was always more than needed before the next appointment (usually 2 months), and subjects were instructed to return unused capsules at that time. Comparison of the number of capsules returned with the number that should have been returned indicated that the DHA group took a mean of 2.9 ± 0.3 capsules, rather than the prescribed 3 capsules per day, and the placebo group took a mean of 3.0 ± 0.2 capsules per day. The investigation was approved by the Institutional Review Board of Baylor College of Medicine and Affiliated
Hospitals. Assent of the child and written informed consent of at least one parent were obtained before enrollment.
Plasma Phospholipid Fatty Acid Patterns Plasma phospholipid fatty acid patterns were measured at baseline and at the end of the study. Plasma lipids were extracted by the method of Bligh and Dyer.25 The phospholipid fraction was separated by one-dimensional thin-layer chromatography (Silica gel G) with hexane, diethyl ether, and glacial acetic acid (70/35/1 by volume); and methyl esters of the component fatty acids of the phospholipid fraction, prepared with boron trifluoride-methanol,26 were quantified by gas-liquid chromatography (Varian 3500, Walnut Creek, Calif) by using a DB-225 capillary column (J & W Scientific, Folsom, Calif) in the presence of 17:0 and 21:0 internal standards.
Measures of Attention and Impulsivity Objective changes in ADHD symptoms incident to DHA supplementation or placebo were assessed by changes in scores on the Test of Variables of Attention (TOVA)27,28 and the Children’s Color Trails test29,30 from baseline to the end of the study. The TOVA is an age- and gendernormed, computer-administered procedure that measures sustained attention.28 The test requires responses to 2 visually presented figures, a target and a non-target. The subject is instructed to press an electronic microswitch when the target appears and not to press the switch when the non-target appears. Important scores derived from the test include errors of omission (failure to press the switch when the target appears), errors of commission (pressing the switch when the non-target appears), response time (speed at which the subject correctly responds to the visual target), and response time variability (SD of the response time). Errors of omission are considered a measure of
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THE JOURNAL OF PEDIATRICS VOLUME 139, NUMBER 2 inattention, and errors of commission are considered a measure of impulsivity. The Children’s Color Trails test, a measure of alternating visual attention, sequencing, psychomotor speed, and cognitive flexibility, consists of 2 parts.29 In the first part (Color Trails 1), the subject uses a pencil to connect in ascending, sequential order and as rapidly as possible pink or yellow circles with numerals 1 through 15, regardless of the color of the circle. In Color Trails 2, the subject connects the numbered circles in ascending sequence and as rapidly as possible, alternating between pink and yellow circles. Scores are based on the time required to complete each part of the test and the number of errors made on each part. Neither the TOVA nor the Color Trails test is diagnostic of ADHD. However, the TOVA and other continuous performance tests detect responses of children with ADHD to medication,31 and abnormal trail making test scores have been shown to be predictive of ADHD.30,32 Two parental behavioral rating scales, the Child Behavior Checklist (CBCL)33 and the Conners’ Rating Scales,34 were also used. Both are ageand gender-normed instruments that quantify subjective ratings of children’s behavior. The CBCL includes scores for internalizing problem behaviors (eg, withdrawal, somatic complaints, anxiety, and depression); externalizing problem behaviors (eg, delinquent and aggressive behavior); and behaviors related to problems in socialization, thought, and attention. The Conners’ Rating Scale includes scores for hyperactivity, inattention, and oppositional behavior. These behavioral rating scales, although also not diagnostic of ADHD,35 have been used to monitor responses of children with ADHD to medication.36 All subjects were being treated successfully with stimulant medication at the time of enrollment and presented with clear historical evidence of clini-
cally significant impairment in social or academic functioning before administration of medication was started. Thus, stopping the medication for the 4-month duration of this study was not feasible. Rather, stimulant medication was withheld for the 24 hours before administration of the laboratory measures. Because the behavioral effects of methylphenidate, dextroamphetamine, and dextroamphetamine/ amphetamine combinations dissipate within 3 to 8 hours and all are eliminated within 24 hours,36,37 withholding these medications for 24 hours allowed detection of the independent effects of DHA on the laboratory measures of ADHD symptoms. However, parents completed the behavioral rating scales based on observations while the child was receiving stimulant medication plus either DHA or placebo.
Statistical Analysis A change in performance of about 1 SD in components of the TOVA subsequent to administration of stimulant medication is considered clinically significant.28 However, this study was designed to detect a somewhat smaller difference (0.8 SD), which required that 25 subjects assigned to each group complete the 4-month study (power = 80%; P < .05). With an expected dropout rate of at least 20%, all subjects who qualified for enrollment and kept the initial appointment were enrolled (see below). The data presented were obtained from the 54 children who completed all parts of the 4month study. Paired t tests were used to determine whether any changes in outcome variables from baseline to 4 months were statistically significant in either randomized group. Analysis of variance— controlling for age, test scores at baseline, ethnicity, and ADHD subtype— was used to detect statistically significant differences in outcome variables between randomized groups after 4 months of DHA supplementation or placebo administration. This analysis
was done with SPSS statistical software (SPSS Inc, Chicago, Ill) and MINITAB statistics package (MINITAB Inc, State College, Pa). For all analyses, a probability of 5% or less was assumed to represent statistical significance. Regression analysis was used to detect correlations between initial and/or final plasma phospholipid DHA content and initial and/or final scores on the various methods of assessment, as well as between change in plasma phospholipid DHA content over the 4month period of study and changes in scores on each of the various methods of assessment.
RESULTS Subjects Two of the subjects assigned to each group refused to allow one of the venipunctures and were dropped from the study. Five subjects (3 assigned to the DHA group and 2 to the placebo group) were unable to complete the study because of family emergencies. No subject withdrew because of adverse effects of treatment. Thus, 54 subjects (27 per group) completed the 4-month study (Table I). TOVA data at one of the two visits were not available for 5 subjects (2 assigned to the DHA group and 3 assigned to the placebo group) because of computer malfunction during testing, interference, or the subject’s failure to follow instructions; thus, complete TOVA data were available at both baseline and 4 months for only 49 children, 25 assigned to DHA and 24 to placebo. Plasma phospholipid fatty acid patterns and Children’s Color Trails Test scores were available at both baseline and 4 months for all 54 subjects who completed the 4-month study. Parental CBCL and Conners’ Rating Scales were completed at baseline and 4 months for 53 subjects, 27 assigned to DHA and 26 assigned to placebo. There were no statistically significant differences between the two groups. However, there were minor differences 191
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Table I. Description of study subjects
DHA group (n = 27)
Characteristic
Placebo group (n = 27)
Age (y)* 9.1 ± 2.1 Gender (% M/F) 78/22 Race (% white) 100 Methylphenidate dose (mg/d)* 29.2 ± 30.1 (n = 25) Median dose (mg/d) 20.0 Dextroamphetamine dose (mg/d)* 15.0 (n = 1) Amphetamine/dextroamphetamine 10 (n = 1) dose (mg/d)* Treatment duration (mo)* 26.3 ± 21.3 TOVA z scores at baseline†‡ Errors of omission 11.6 ± 2.8 Errors of commission 3.4 ± 0.68 Total response time 1.43 ± 0.25 Response time variability 1.40 ± 0.29 Color Trails Test z scores at baseline*‡ Color Trails 1 0.97 ± 1.58 Color Trails 2 1.21 ± 1.85
9.5 ± 1.7 78/22 85 29.3 ± 17.6 (n = 22) 25.0 16.3 ± 8.8 (n = 2) 15.0 ± 8.7 (n = 3) 29.5 ± 19.9 9.0 ± 3.3 4.0 ± 0.66 1.56 ± 0.27 1.67 ± 0.31 1.37 ± 1.42 1.83 ± 2.62
*Values are expressed as mean ± SD. †Calculated in reference to mean and SD of age- and gender-matched healthy (control) children.27,30 ‡Values are expressed as mean ± SEM.
Table II. Fatty acid pattern of the plasma phospholipid fraction (mol %;) at baseline and after 4 months of DHA supplementation or placebo administration
DHA group (n = 27)
Placebo group (n = 27)
Fatty acid
Baseline
4 months
Baseline
4 months
Total saturated Total monounsaturated Total ω6 18:2 20:4 Total ω3 18:3 20:5 22:5 22:6
47.0 ± 3.6 13.6 ± 2.1 36.0 ± 3.0 23.1 ± 3.5 9.6 ± 1.6 3.36 ± 0.55 0.35 ± 0.26 0.32 ± 0.09 0.74 ± 0.11 1.89 ± 0.45
45.1 ± 2.8 14.3 ± 1.9 34.5 ± 2.7 23.0 ± 3.5 8.4 ± 2.3* 6.17 ± 1.64* 0.29 ± 0.08 0.47 ± 0.61 0.51 ± 0.13* 4.85 ± 1.35*
47.4 ± 3.3 13.5 ± 1.8 35.7 ± 3.1 22.5 ± 2.7 9.9 ± 1.3 3.45 ± 0.68 0.35 ± 0.42 0.33 ± 0.12 0.76 ± 0.16 1.96 ± 0.40
45.1 ± 2.2 14.1 ± 1.8 37.5 ± 2.1 24.4 ± 2.3 9.6 ± 1.1 3.32 ± 0.85 0.31 ± 0.09 0.38 ± 0.16 0.73 ± 0.17 1.86 ± 0.87
Values are expressed as mean ± SD. *P < .05, baseline versus 4 months.
between groups in age and ethnicity. There also were some minor differences in ADHD subtypes between the two groups. Twenty-two (81%) of those assigned to the DHA group met DSM-IV criteria for ADHD, combined type; and 5 (19%) met criteria for ADHD, predominantly inattentive 192
type. All 26 subjects assigned to the placebo group met DSM-IV criteria for ADHD, combined type. DSM-IV criteria for oppositional defiant disorder were met by 13 (48%) of the subjects assigned to DHA and by 15 (55%) of the subjects assigned to placebo. DSM-IV criteria for conduct disor-
der were met by 6 (22%) of the subjects assigned to DHA and by 2 (7%) of the subjects assigned to placebo. These minor differences in age, ethnicity, and ADHD subtype between groups were controlled for in the statistical analysis of all outcome variables. As illustrated by the mean baseline z scores (calculated from the mean and SD of age- and gender-matched asymptomatic children),28,30 both groups had elevated mean scores on all components of the TOVA and on both Children’s Color Trails Tests (Table I).
Fatty Acid Pattern of the Plasma Phospholipid Fraction As expected,22,23 the plasma phospholipid contents of DHA and arachidonic acid (20:4ω6) were low in both groups at baseline (Table II). After 4 months, the plasma phospholipid DHA content of the placebo group remained low, whereas that of the DHA group had increased by 260% (P < .001). This increase in plasma phospholipid DHA content was accompanied by a 12.5% decline in the plasma phospholipid content of arachidonic acid (P = .13) and an approximately 30% decline in the plasma phospholipid content of 22:5ω3 (P < .001).
Laboratory Measures of Attention and Impulsivity Table III shows the mean scores of each group on each component of the TOVA at baseline and at the end of the study. Both groups made more errors of omission but fewer errors of commission after 4 months of either DHA or placebo treatment than at baseline. The increase in errors of omission by the DHA group was statistically significant (P = .013), but the increase by the placebo group was not (P = .70). In contrast, the decrease in errors of commission by the placebo group over the 4-month period was statistically significant (P = .0002), but the decrease by the DHA group was not. Both groups also took longer to respond after 4 months than at baseline and had
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THE JOURNAL OF PEDIATRICS VOLUME 139, NUMBER 2 greater response time variability. The placebo group’s increase in response time from baseline to 4 months was statistically significant (P = .029), but that of the DHA group was borderline (P = .071). The small increase in response time variability observed in both groups was not statistically significant in either group. Thus, over time, inattention increased in both groups (more errors of omission, longer response times, and more variability in response time), and impulsivity decreased (fewer commission errors). However, there were no statistically significant differences between groups in scores on any component of the TOVA after 4 months of DHA supplementation compared with placebo. There were no statistically significant correlations between initial plasma phospholipid DHA content and initial scores on any component of the TOVA (r = –0.018-0.16 [range]), between final plasma phospholipid DHA content and final scores on any component of the TOVA (r = –0.162-0.056), or between the change in plasma phospholipid DHA content from baseline to 4 months and the change in scores on any component of the TOVA during this time (r = 0.288-0.299). Scores of the Children’s Color Trails Test improved from baseline to 4 months in both groups, as evidenced by the fact that less time was required for completion after 4 months of DHA or placebo treatment (except for Color Trails 1) than at baseline (Table III). The better scores after 4 months, compared with scores at baseline, may represent improved sustained attention for both groups, but more likely represent a learning effect, a recognized limitation of the Color Trails Test.29 As with the TOVA scores, there was no statistically significant difference between groups in scores on either Children’s Color Trails Test after 4 months of DHA supplementation compared with placebo. There were also no statistically significant correlations between initial
Table III. Mean TOVA and Color Trails scores at baseline and after 4 months of DHA supplementation or placebo administration
TOVA Errors of omission DHA (n = 25) Placebo (n = 24) Errors of commission DHA (n = 25) Placebo (n = 24) Total response time (ms) DHA (n = 25) Placebo (n = 24) Response time variability (ms) DHA (n = 25) Placebo (n = 24) Color Trails Color Trails 1 (s) DHA (n = 27) Placebo (n = 27) Color Trails 2 (s) DHA (n = 27) Placebo (n = 27)
Baseline
4 Months
33.6 ± 7.6 37.0 ± 13.3
56.0 ± 12.8* 41.5 ± 10.6
24.5 ± 4.2 26.1 ± 3.1
20.8 ± 4.6 12.5 ± 2.8†
598.2 ± 25.4 562.5 ± 21.5
637.6 ± 30.6 610.0 ± 25.4*
223.9 ± 15.2 215.9 ± 13.6
240.3 ± 17.6 217.3 ± 14.9
33.9 ± 2.3 28.9 ± 2.1
29.4 ± 2.8* 26.2 ± 2.4
74.6 ± 7.3 67.3 ± 5.3
52.9 ± 4.8‡ 50.5 ± 3.7†
Values are expressed as mean ± SEM. *Difference from baseline value is statistically significant (P = .03-.01). †Difference from baseline value is statistically significant (P < .0003). ‡Difference from baseline value is statistically significant (P = .001).
plasma phospholipid DHA content and initial scores on any component of the Children’s Color Trails Test (r = 0.056-0.094), between plasma phospholipid DHA content after 4 months of DHA or placebo treatment and final scores on any component (r = 0.103-0.153), or between the change in plasma phospholipid DHA content from baseline to 4 months and change in scores on any component (r = –0.185-0.083) during this period. Mean scores for all behaviors assessed by the parental CBCL (Table IV) tended to decrease from baseline to 4 months, but none of these changes was statistically significant in either group. There were also no statistically significant differences between groups in any of the behaviors assessed after 4 months of DHA supplementation compared with placebo. Further, there were no differences between groups at any time on any behavior measured by
the parental Conners’ Rating Scales (data not shown).
DISCUSSION Epidemiologic data suggest that populations with lower ω3 fatty acid consumption and, hence, lower plasma and, presumably, tissue contents of ω3 fatty acids, including DHA, have higher rates of psychiatric disorders.38 There is a direct relationship between plasma phospholipid DHA content and metabolism of serotonin and dopamine within the central nervous system.39,40 In addition, DHA and other long-chain polyunsaturated fatty acids may influence synaptic function directly through effects on membrane structure, as well as indirectly through the generation of eicosanoids (prostaglandins, leukotrienes, thromboxanes) or through immune system/cytokine interactions. Thus, there 193
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Table IV. Parental CBCL T-scores* at baseline and after 4 months of DHA or placebo treatment
Internalizing behaviors DHA (n = 27) Placebo (n = 26) Externalizing behaviors DHA (n = 27) Placebo (n = 26) Socialization problems DHA (n = 27) Placebo (n = 26) Thought problems DHA (n = 27) Placebo (n = 26) Attention problems DHA (n = 27) Placebo (n = 26)
Baseline
4 Months
58.2 ± 2.4 54.9 ± 2.1
53.1 ± 2.1 51.2 ± 1.5
62.6 ± 2.1 58.5 ± 2.3
58.5 ± 2.1 56.3 ± 2.2
61.5 ± 1.9 58.6 ± 1.6
56.7 ± 1.6 56.3 ± 1.5
60.1 ± 1.9 56.2 ± 1.4
56.8 ± 1.5 56.5 ± 1.5
68.2 ± 2.1 64.3 ± 1.2
64.4 ± 1.9 60.9 ± 1.6
Values are expressed as mean ± SEM. *A T-score >70 indicates a clinically significant behavioral problem.
has been considerable interest in the potential role of long-chain polyunsaturated fatty acids in the etiology and treatment of a variety of psychiatric disorders, such as impulsive violence,40 depression,41 aggression,42 and bipolar disorder,43 as well as ADHD of childhood.22,23,44-46 In two prior studies,45,46 no consistent improvement in behavior of children with ADHD was observed incident to supplementation with evening primrose oil (a concentrated source of 18:3ω6, which can be converted to arachidonic acid (20:4ω6)). However, the effect of supplementation with ω3 long-chain polyunsaturated fatty acids on the symptoms of ADHD has not been studied previously. As observed by others,22,23 the children with ADHD who participated in the study reported here had low levels of plasma phospholipid DHA at baseline and, as expected, supplementation with DHA (345 mg/d) for 4 months increased plasma phospholipid DHA content. However, despite the approximately 2.6-fold increase in plasma phospholipid DHA incident to DHA supplementation, there were no statis194
tically significant differences between groups in any laboratory measure of ADHD symptoms or in any component of two parental behavioral scales after 4 months of DHA supplementation compared with placebo. In fact, errors of omission, a TOVA component that reflects inattention, increased significantly in the DHA group but not in the placebo group, and errors of commission, a TOVA component that reflects impulsivity, decreased significantly in the placebo group but not in the DHA group. The lack of an effect of DHA supplementation on ADHD symptoms does not necessarily mean that a low brain or synaptic content of DHA is not involved in the etiology of ADHD. Because the turnover of fatty acids in the brain is likely to be quite low in 6- to 12-year-old children, a longer period of supplementation and/or a larger amount of supplement might be required to alter the fatty acid content of the central nervous system. It is also possible, as reported for piglets,47 that the plasma phospholipid content of DHA is a poor reflector of brain or synaptic DHA content. In isolated cell systems, α-linolenic acid
(18:3ω3), the obligate precursor of DHA, as well as other desaturated and elongated products of 18:3ω3 are taken up by cerebral microvascular endothelial cells and converted to DHA by astrocytes, which in turn release DHA for uptake by neurons.48-50 If a similar process is involved in vivo, the level of brain DHA could be largely independent of the plasma lipid level of DHA. However, supplementation with fish oil, which contains precursors of DHA, or with α-linolenic acid, which results in higher plasma lipid levels of these precursors, as well as DHA, might be a more effective treatment. The possibility that the amount of DHA in synaptic membranes has no effect on synaptic transmission or that the DHA content of synaptic membranes does not influence the specific neurotransmitter systems involved in the genesis of ADHD must also be considered. In addition, it is important to remember that the plasma phospholipid content of arachidonic acid is also low in children with ADHD and decreases further with DHA supplementation. Thus, any future study of the effect of DHA on ADHD symptoms should include supplementation with both arachidonic acid and DHA. Future studies must evaluate the same or a higher dose of DHA given for a longer period, supplementation with other ω3 fatty acids, and/or supplementation with a combination of ω3 and ω6 fatty acids. The possibility that more optimal DHA intake during early life may decrease the prevalence of ADHD should also be evaluated. However, it is clear from the data presented here that DHA supplementation for 4 months did not ameliorate the symptoms of ADHD. Thus, these data do not support the efficacy of DHA supplementation, as provided in this study, as an alternative or adjunctive treatment for ADHD. We gratefully acknowledge the assistance of C. Boutte, Study Coordinator, the editorial advice of L. Loddeke, and the secretarial expertise of R. Newsom.
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tion. Can J Biochem Physiol 1959;37: 911-7. Morrison WR, Smith LM. Preparation of fatty acid methyl esters and dimethyl acetals from lipids with boron fluoride-methanol. J Lipid Res 1964; 5:600-8. Greenberg LM, Walden ID. Developmental normative data on the test of variables of attention (TOVA). J Am Acad Child Adolesc Psychol 1993;34: 1019-30. Greenberg LM, Kindschi CL. T.O.V.A. Test of Variables of Attention: clinical guide. Los Alamitos (CA): Universal Attention Disorders Inc; 1996. D’Elia LF, Satz P, Uchiyama CL, White T. Color Trails Test 1 & 2. Odessa (FL): Psychological Assessment Resources; 1994. Williams J, Rickert V, Hogan J, Zolten AJ, Satz P, D’Elia LF, et al. Children’s Color Trails. Arch Clin Neuropsychol 1995;10:211-23. Fischer M, Newby R. Assessment of stimulant response in ADHD children using a refined multimethod clinical protocol. J Clin Child Psychol 1991; 20:232-44. Barkley RA, Grodzinsky G. Are tests of frontal lobe function useful in the diagnosis of attention deficit disorders? Clin Neuropsychol 1994;8:121- 39. Achenbach TM, Edelbrock KC. Manual for the Child Behavior Checklist and Revised Child Behavior Profile. Burlington (VT): University of Vermont Department of Psychiatry; 1983. Goyette CH, Conners CK, Ulrich RF. Normative data on the revised Conners’ parent & teacher rating scales. J Abnorm Child Psychol 1978;6:221-36. Accardo PJ, Whitman BY. The misdiagnosis of the hyperactive child. In: Accardo PJ, Blondis TA, Whitman BY, editors. Attention deficit disorders and hyperactivity in children. New York: Marcel Dekker; 1991. p. 1-26. Dupaul GJ, Barkley RA, Connor DF. Stimulants. In: Barkley RA, editor. Attention-deficit hyperactivity disorder: a handbook for diagnosis and treatment. 2nd ed. New York: Guilford Publications; 1998. p. 510-51. Swanson JM, Wigal S, Greenhill LL, Browne R, Waslik B, Lerner M, et al. Analog classroom assessment of Adderall in children with ADHD. J Am Acad Child Adolesc Psychiatry 1998;37:519-26. Hibbeln JR. Apparent fish consump195
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tion and the prevalence of major depression: a cross-national perspective [letter]. Lancet 1998;351:1213. Hibbeln JR, Linnoila M, Umhau JC, Rawlings R, George DT, Salem NS. Essential fatty acids predict metabolites of serotonin and dopamine in cerebrospinal fluid among healthy control subjects, and early and late onset alcoholics. Biol Psychiatry 1998;44:235-42. Hibbeln JR, Umhau JC, Linnoila M, George DT, Regan P, Shoaf S, et al. A replication study of violent and nonviolent subjects: CSF metabolites of serotonin and dopamine are predicted by plasma essential fatty acids. Biol Psychiatry 1998;44:243-9. Hibbeln JR, Salem N. Dietary polyunsaturated fatty acids and depression: when cholesterol does not satisfy. Am J Clin Nutr 1995;62:1-9. Hamazaki T, Sawazaki S, Itomura M,
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Assoka E, Nagao Y, Nishimura N, et al. The effect of docosahexaenoic acid on aggression in young adults. J Clin Invest 1996;97:1129-33. Stoll AL, Severus WE, Freeman MP, Rueter S, Zboyan MA, Diamond E, et al. Omega 3 fatty acids and bipolar disorder: a preliminary double-blind placebo-controlled trial. Arch Gen Psychiatry 1999;56:407-12. Colquhoun I, Bunday S. A lack of essential fatty acids as a possible cause of hyperactivity in children. Med Hypothesis 1981;7:673-9. Aman MG, Mitchell EA, Turbott SH. The effects of essential fatty acid supplementation by Efamol in hyperactive children. J Abnorm Child Psychol 1987;15:75-90. Arnold EC, Kleykamp D, Votolato NA, Taylor WA, Kontras SB, Tobin K. Gamma-linolenic acid for attentiondeficit hyperactivity disorder: placebo
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controlled comparison to d-amphetamine. Biol Psychiatry 1989;25:222-8. Rioux FM, Innis SM, Dyer R, MacKinnon M. Diet-induced changes in liver and bile but not brain fatty acids can be predicted from differences in plasma phospholipid fatty acids in formula and milk fed piglets. J Nutr 1997;127:370-7. Moore SA, Yoder E, Spector AA. Role of the blood-brain barrier in the formation of long-chain ω-3 and ω-6 fatty acids from essential fatty acid precursors. J Neurochem 1990;55:391-402. Moore SA, Yoder E, Murphy S, Dutton GR, Spector AA. Astrocytes, not neurons, produce docosahexaenoic acid (22:6ω3) and arachidonic acid (20: 4ω6). J Neurochem 1991;56:518-24. Moore SA. Cerebral endothelium and astrocytes cooperate in supplying docosahexaenoic acid to neurons. Adv Exp Med Biol 1993;331:229-33.
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A randomized, double-blind, placebo-controlled trial of docosahexaenoic acid supplementation in children with attention-deficit/hyperactivity disorder Robert G. Voigt, MD, Antolin M. Llorente, PhD, Craig L. Jensen, MD, J. Kennard Fraley, MPH, Marcia C. Berretta, LMSW, and William C. Heird, MD Objective: To determine whether docosahexaenoic acid (DHA) supplementation for 4 months decreases the symptoms of attention-deficit/hyperactivity disorder (ADHD). Study design: Sixty-three 6- to-12-year-old children with ADHD, all receiving effective maintenance therapy with stimulant medication, were assigned randomly, in a double-blind fashion, to receive DHA supplementation (345 mg/d) or placebo for 4 months. Outcome variables included plasma phospholipid fatty acid patterns, scores on laboratory measures of inattention and impulsivity (Test of Variables of Attention, Children’s Color Trails test) while not taking stimulant medication, and scores on parental behavioral rating scales (Child Behavior Checklist, Conners’ Rating Scale). Differences between groups after 4 months of DHA supplementation or placebo administration were determined by analysis of variance, controlling for age, baseline value of each outcome variable, ethnicity, and ADHD subtype. Results: Plasma phospholipid DHA content of the DHA-supplemented group was 2.6-fold higher at the end of the study than that of the placebo group (4.85 ± 1.35 vs 1.86 ± 0.87 mol % of total fatty acids; P < .001). Despite this, there was no statistically significant improvement in any objective or subjective measure of ADHD symptoms. Conclusion: A 4-month period of DHA supplementation (345 mg/d) does not decrease symptoms of ADHD. (J Pediatr 2001;139:189-96) From the Division of Developmental and Behavioral Pediatrics, Mayo Clinic, Rochester, Minnesota; Departments of Pediatrics, Psychiatry, and the US Department of Agriculture, Agricultural Research Service Children’s Nutrition Research Center, Baylor College of Medicine, Houston, Texas.
This work is a publication of the US Department of Agriculture, Agricultural Research Service (USDA/ARS) Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, and has been funded in part with federal funds from the US Department of Agriculture, Agricultural Research Service, under Cooperative Agreement No. 386250-1-003. The contents of this publication do not necessarily reflect the views or policies of the US Department of Agriculture, nor does the mention of trade names, commercial products, or organizations imply endorsement by the United States Government. This study was also funded in part by a grant from the Martek Biosciences Corporation, Columbia, Maryland, which, in addition, provided the docosahexaenoic acid (DHA) and placebo capsules used in the study. Submitted for publication Nov 7, 2000; revision received Feb 1, 2001; accepted Mar 23, 2001. Reprint requests: Robert G. Voigt, MD, Division of Developmental and Behavioral Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, 200 First St SW, Baldwin 3A, Rochester, MN 55905. 9/21/116050 doi:10.1067/mpd.2001.116050
Attention-deficit/hyperactivity disorder (ADHD),1 characterized by developmentally inappropriate and disabling levels of inattention, impulsivity, and/or hyperactivity, is one of
See editorial, p 173. the most common chronic health conditions affecting school-aged children.2,3 Although 70% to 90% of children with ADHD respond positively to treatment with stimulant medications (eg, methylphenidate and dexADHD
Attention-deficit/hyperactivity disorder CBCL Child Behavior Checklist DHA Docosahexaenoic acid DSM-IV Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition TOVA Test of Variables of Attention
troamphetamine sulfate),3,4 there is considerable concern regarding potential adverse consequences of protracted use of these medications,5-10 particularly because data showing that stimulant medication improves the long-term prognosis of children with ADHD are scarce.11-15 Therefore, alternative treatments for ADHD are widely used.16 Currently, there is considerable interest in the possibility that dietary supplementation with the long-chain, polyunsaturated fatty acid, docosahexaenoic acid (DHA [22:6ω3]), will decrease the symptoms of ADHD. DHA is present in large amounts in 189
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the structural lipids of brain cell membranes, including those of the synaptic terminals,17-21 and children with ADHD have been shown to have low plasma and erythrocyte phospholipid levels of DHA.22,23 Assuming that brain levels also are low, it has been argued that DHA supplementation will increase levels and that the resulting alterations in synaptic transmission will decrease the symptoms of ADHD. Indeed, despite a lack of data to support either efficacy or safety, DHA supplements are readily available and are being marketed for the treatment of children with ADHD.16 The objective of this study was to determine the efficacy of DHA supplementation in reducing symptoms of ADHD.
medication, underwent a confirmatory diagnostic interview with a neurodevelopmental pediatrician to confirm responses to the telephone interview and to ensure that each met strict Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)1 criteria for ADHD and had clear historical evidence of clinically significant impairment in social or academic functioning. Children who met DSM-IV criteria for oppositional defiant disorder or conduct disorder, both of which are common comorbid conditions in children with ADHD,24 were not excluded. Seventy of the 90 potential subjects who completed the diagnostic interview were considered to have idiopathic ADHD and were offered study enrollment; 63 returned for randomization.
METHODS
Randomization
Subjects Parents or guardians of 250 children who responded to advertisements for study volunteers were screened by telephone. A total of 160 children were excluded for one or more of the following reasons: (1) ineffective treatment with stimulant medication; (2) treatment with other psychotropic medications; (3) previous diagnosis of other childhood psychiatric disorders (ie, anxiety, mood, thought, or bipolar disorders), (4) use of dietary supplements other than vitamins, (5) occurrence of a significant life event (eg, death of an immediate family member, parental separation or divorce, or relocation) within 6 months; (6) a history of head injury or seizures; (7) receipt of special education services for mental retardation or a pervasive developmental disorder; (8) premature birth; (9) exposure to tobacco, alcohol, or other drugs in utero; and/or (10) diagnosis of a disorder of lipid metabolism or other chronic medical condition. The remaining 90 children, all of whom had previously been given a diagnosis of ADHD by a physician and were being treated successfully with stimulant 190
All subjects were randomly assigned in a double-blind fashion according to a computer-generated randomization scheme to receive either an algae-derived triglyceride capsule (DHASCO; Martek Biosciences Corporation, Columbia, Md), providing 345 mg of DHA per day (n = 32), or a placebo capsule (n = 31) for 4 months. Both capsules were provided by Martek Biosciences Corporation and were identical in appearance. They were dispensed by the Investigational Pharmacy of Texas Children’s Hospital according to the computer-generated randomization scheme. The number of capsules dispensed was always more than needed before the next appointment (usually 2 months), and subjects were instructed to return unused capsules at that time. Comparison of the number of capsules returned with the number that should have been returned indicated that the DHA group took a mean of 2.9 ± 0.3 capsules, rather than the prescribed 3 capsules per day, and the placebo group took a mean of 3.0 ± 0.2 capsules per day. The investigation was approved by the Institutional Review Board of Baylor College of Medicine and Affiliated
Hospitals. Assent of the child and written informed consent of at least one parent were obtained before enrollment.
Plasma Phospholipid Fatty Acid Patterns Plasma phospholipid fatty acid patterns were measured at baseline and at the end of the study. Plasma lipids were extracted by the method of Bligh and Dyer.25 The phospholipid fraction was separated by one-dimensional thin-layer chromatography (Silica gel G) with hexane, diethyl ether, and glacial acetic acid (70/35/1 by volume); and methyl esters of the component fatty acids of the phospholipid fraction, prepared with boron trifluoride-methanol,26 were quantified by gas-liquid chromatography (Varian 3500, Walnut Creek, Calif) by using a DB-225 capillary column (J & W Scientific, Folsom, Calif) in the presence of 17:0 and 21:0 internal standards.
Measures of Attention and Impulsivity Objective changes in ADHD symptoms incident to DHA supplementation or placebo were assessed by changes in scores on the Test of Variables of Attention (TOVA)27,28 and the Children’s Color Trails test29,30 from baseline to the end of the study. The TOVA is an age- and gendernormed, computer-administered procedure that measures sustained attention.28 The test requires responses to 2 visually presented figures, a target and a non-target. The subject is instructed to press an electronic microswitch when the target appears and not to press the switch when the non-target appears. Important scores derived from the test include errors of omission (failure to press the switch when the target appears), errors of commission (pressing the switch when the non-target appears), response time (speed at which the subject correctly responds to the visual target), and response time variability (SD of the response time). Errors of omission are considered a measure of
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THE JOURNAL OF PEDIATRICS VOLUME 139, NUMBER 2 inattention, and errors of commission are considered a measure of impulsivity. The Children’s Color Trails test, a measure of alternating visual attention, sequencing, psychomotor speed, and cognitive flexibility, consists of 2 parts.29 In the first part (Color Trails 1), the subject uses a pencil to connect in ascending, sequential order and as rapidly as possible pink or yellow circles with numerals 1 through 15, regardless of the color of the circle. In Color Trails 2, the subject connects the numbered circles in ascending sequence and as rapidly as possible, alternating between pink and yellow circles. Scores are based on the time required to complete each part of the test and the number of errors made on each part. Neither the TOVA nor the Color Trails test is diagnostic of ADHD. However, the TOVA and other continuous performance tests detect responses of children with ADHD to medication,31 and abnormal trail making test scores have been shown to be predictive of ADHD.30,32 Two parental behavioral rating scales, the Child Behavior Checklist (CBCL)33 and the Conners’ Rating Scales,34 were also used. Both are ageand gender-normed instruments that quantify subjective ratings of children’s behavior. The CBCL includes scores for internalizing problem behaviors (eg, withdrawal, somatic complaints, anxiety, and depression); externalizing problem behaviors (eg, delinquent and aggressive behavior); and behaviors related to problems in socialization, thought, and attention. The Conners’ Rating Scale includes scores for hyperactivity, inattention, and oppositional behavior. These behavioral rating scales, although also not diagnostic of ADHD,35 have been used to monitor responses of children with ADHD to medication.36 All subjects were being treated successfully with stimulant medication at the time of enrollment and presented with clear historical evidence of clini-
cally significant impairment in social or academic functioning before administration of medication was started. Thus, stopping the medication for the 4-month duration of this study was not feasible. Rather, stimulant medication was withheld for the 24 hours before administration of the laboratory measures. Because the behavioral effects of methylphenidate, dextroamphetamine, and dextroamphetamine/ amphetamine combinations dissipate within 3 to 8 hours and all are eliminated within 24 hours,36,37 withholding these medications for 24 hours allowed detection of the independent effects of DHA on the laboratory measures of ADHD symptoms. However, parents completed the behavioral rating scales based on observations while the child was receiving stimulant medication plus either DHA or placebo.
Statistical Analysis A change in performance of about 1 SD in components of the TOVA subsequent to administration of stimulant medication is considered clinically significant.28 However, this study was designed to detect a somewhat smaller difference (0.8 SD), which required that 25 subjects assigned to each group complete the 4-month study (power = 80%; P < .05). With an expected dropout rate of at least 20%, all subjects who qualified for enrollment and kept the initial appointment were enrolled (see below). The data presented were obtained from the 54 children who completed all parts of the 4month study. Paired t tests were used to determine whether any changes in outcome variables from baseline to 4 months were statistically significant in either randomized group. Analysis of variance— controlling for age, test scores at baseline, ethnicity, and ADHD subtype— was used to detect statistically significant differences in outcome variables between randomized groups after 4 months of DHA supplementation or placebo administration. This analysis
was done with SPSS statistical software (SPSS Inc, Chicago, Ill) and MINITAB statistics package (MINITAB Inc, State College, Pa). For all analyses, a probability of 5% or less was assumed to represent statistical significance. Regression analysis was used to detect correlations between initial and/or final plasma phospholipid DHA content and initial and/or final scores on the various methods of assessment, as well as between change in plasma phospholipid DHA content over the 4month period of study and changes in scores on each of the various methods of assessment.
RESULTS Subjects Two of the subjects assigned to each group refused to allow one of the venipunctures and were dropped from the study. Five subjects (3 assigned to the DHA group and 2 to the placebo group) were unable to complete the study because of family emergencies. No subject withdrew because of adverse effects of treatment. Thus, 54 subjects (27 per group) completed the 4-month study (Table I). TOVA data at one of the two visits were not available for 5 subjects (2 assigned to the DHA group and 3 assigned to the placebo group) because of computer malfunction during testing, interference, or the subject’s failure to follow instructions; thus, complete TOVA data were available at both baseline and 4 months for only 49 children, 25 assigned to DHA and 24 to placebo. Plasma phospholipid fatty acid patterns and Children’s Color Trails Test scores were available at both baseline and 4 months for all 54 subjects who completed the 4-month study. Parental CBCL and Conners’ Rating Scales were completed at baseline and 4 months for 53 subjects, 27 assigned to DHA and 26 assigned to placebo. There were no statistically significant differences between the two groups. However, there were minor differences 191
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Table I. Description of study subjects
DHA group (n = 27)
Characteristic
Placebo group (n = 27)
Age (y)* 9.1 ± 2.1 Gender (% M/F) 78/22 Race (% white) 100 Methylphenidate dose (mg/d)* 29.2 ± 30.1 (n = 25) Median dose (mg/d) 20.0 Dextroamphetamine dose (mg/d)* 15.0 (n = 1) Amphetamine/dextroamphetamine 10 (n = 1) dose (mg/d)* Treatment duration (mo)* 26.3 ± 21.3 TOVA z scores at baseline†‡ Errors of omission 11.6 ± 2.8 Errors of commission 3.4 ± 0.68 Total response time 1.43 ± 0.25 Response time variability 1.40 ± 0.29 Color Trails Test z scores at baseline*‡ Color Trails 1 0.97 ± 1.58 Color Trails 2 1.21 ± 1.85
9.5 ± 1.7 78/22 85 29.3 ± 17.6 (n = 22) 25.0 16.3 ± 8.8 (n = 2) 15.0 ± 8.7 (n = 3) 29.5 ± 19.9 9.0 ± 3.3 4.0 ± 0.66 1.56 ± 0.27 1.67 ± 0.31 1.37 ± 1.42 1.83 ± 2.62
*Values are expressed as mean ± SD. †Calculated in reference to mean and SD of age- and gender-matched healthy (control) children.27,30 ‡Values are expressed as mean ± SEM.
Table II. Fatty acid pattern of the plasma phospholipid fraction (mol %;) at baseline and after 4 months of DHA supplementation or placebo administration
DHA group (n = 27)
Placebo group (n = 27)
Fatty acid
Baseline
4 months
Baseline
4 months
Total saturated Total monounsaturated Total ω6 18:2 20:4 Total ω3 18:3 20:5 22:5 22:6
47.0 ± 3.6 13.6 ± 2.1 36.0 ± 3.0 23.1 ± 3.5 9.6 ± 1.6 3.36 ± 0.55 0.35 ± 0.26 0.32 ± 0.09 0.74 ± 0.11 1.89 ± 0.45
45.1 ± 2.8 14.3 ± 1.9 34.5 ± 2.7 23.0 ± 3.5 8.4 ± 2.3* 6.17 ± 1.64* 0.29 ± 0.08 0.47 ± 0.61 0.51 ± 0.13* 4.85 ± 1.35*
47.4 ± 3.3 13.5 ± 1.8 35.7 ± 3.1 22.5 ± 2.7 9.9 ± 1.3 3.45 ± 0.68 0.35 ± 0.42 0.33 ± 0.12 0.76 ± 0.16 1.96 ± 0.40
45.1 ± 2.2 14.1 ± 1.8 37.5 ± 2.1 24.4 ± 2.3 9.6 ± 1.1 3.32 ± 0.85 0.31 ± 0.09 0.38 ± 0.16 0.73 ± 0.17 1.86 ± 0.87
Values are expressed as mean ± SD. *P < .05, baseline versus 4 months.
between groups in age and ethnicity. There also were some minor differences in ADHD subtypes between the two groups. Twenty-two (81%) of those assigned to the DHA group met DSM-IV criteria for ADHD, combined type; and 5 (19%) met criteria for ADHD, predominantly inattentive 192
type. All 26 subjects assigned to the placebo group met DSM-IV criteria for ADHD, combined type. DSM-IV criteria for oppositional defiant disorder were met by 13 (48%) of the subjects assigned to DHA and by 15 (55%) of the subjects assigned to placebo. DSM-IV criteria for conduct disor-
der were met by 6 (22%) of the subjects assigned to DHA and by 2 (7%) of the subjects assigned to placebo. These minor differences in age, ethnicity, and ADHD subtype between groups were controlled for in the statistical analysis of all outcome variables. As illustrated by the mean baseline z scores (calculated from the mean and SD of age- and gender-matched asymptomatic children),28,30 both groups had elevated mean scores on all components of the TOVA and on both Children’s Color Trails Tests (Table I).
Fatty Acid Pattern of the Plasma Phospholipid Fraction As expected,22,23 the plasma phospholipid contents of DHA and arachidonic acid (20:4ω6) were low in both groups at baseline (Table II). After 4 months, the plasma phospholipid DHA content of the placebo group remained low, whereas that of the DHA group had increased by 260% (P < .001). This increase in plasma phospholipid DHA content was accompanied by a 12.5% decline in the plasma phospholipid content of arachidonic acid (P = .13) and an approximately 30% decline in the plasma phospholipid content of 22:5ω3 (P < .001).
Laboratory Measures of Attention and Impulsivity Table III shows the mean scores of each group on each component of the TOVA at baseline and at the end of the study. Both groups made more errors of omission but fewer errors of commission after 4 months of either DHA or placebo treatment than at baseline. The increase in errors of omission by the DHA group was statistically significant (P = .013), but the increase by the placebo group was not (P = .70). In contrast, the decrease in errors of commission by the placebo group over the 4-month period was statistically significant (P = .0002), but the decrease by the DHA group was not. Both groups also took longer to respond after 4 months than at baseline and had
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THE JOURNAL OF PEDIATRICS VOLUME 139, NUMBER 2 greater response time variability. The placebo group’s increase in response time from baseline to 4 months was statistically significant (P = .029), but that of the DHA group was borderline (P = .071). The small increase in response time variability observed in both groups was not statistically significant in either group. Thus, over time, inattention increased in both groups (more errors of omission, longer response times, and more variability in response time), and impulsivity decreased (fewer commission errors). However, there were no statistically significant differences between groups in scores on any component of the TOVA after 4 months of DHA supplementation compared with placebo. There were no statistically significant correlations between initial plasma phospholipid DHA content and initial scores on any component of the TOVA (r = –0.018-0.16 [range]), between final plasma phospholipid DHA content and final scores on any component of the TOVA (r = –0.162-0.056), or between the change in plasma phospholipid DHA content from baseline to 4 months and the change in scores on any component of the TOVA during this time (r = 0.288-0.299). Scores of the Children’s Color Trails Test improved from baseline to 4 months in both groups, as evidenced by the fact that less time was required for completion after 4 months of DHA or placebo treatment (except for Color Trails 1) than at baseline (Table III). The better scores after 4 months, compared with scores at baseline, may represent improved sustained attention for both groups, but more likely represent a learning effect, a recognized limitation of the Color Trails Test.29 As with the TOVA scores, there was no statistically significant difference between groups in scores on either Children’s Color Trails Test after 4 months of DHA supplementation compared with placebo. There were also no statistically significant correlations between initial
Table III. Mean TOVA and Color Trails scores at baseline and after 4 months of DHA supplementation or placebo administration
TOVA Errors of omission DHA (n = 25) Placebo (n = 24) Errors of commission DHA (n = 25) Placebo (n = 24) Total response time (ms) DHA (n = 25) Placebo (n = 24) Response time variability (ms) DHA (n = 25) Placebo (n = 24) Color Trails Color Trails 1 (s) DHA (n = 27) Placebo (n = 27) Color Trails 2 (s) DHA (n = 27) Placebo (n = 27)
Baseline
4 Months
33.6 ± 7.6 37.0 ± 13.3
56.0 ± 12.8* 41.5 ± 10.6
24.5 ± 4.2 26.1 ± 3.1
20.8 ± 4.6 12.5 ± 2.8†
598.2 ± 25.4 562.5 ± 21.5
637.6 ± 30.6 610.0 ± 25.4*
223.9 ± 15.2 215.9 ± 13.6
240.3 ± 17.6 217.3 ± 14.9
33.9 ± 2.3 28.9 ± 2.1
29.4 ± 2.8* 26.2 ± 2.4
74.6 ± 7.3 67.3 ± 5.3
52.9 ± 4.8‡ 50.5 ± 3.7†
Values are expressed as mean ± SEM. *Difference from baseline value is statistically significant (P = .03-.01). †Difference from baseline value is statistically significant (P < .0003). ‡Difference from baseline value is statistically significant (P = .001).
plasma phospholipid DHA content and initial scores on any component of the Children’s Color Trails Test (r = 0.056-0.094), between plasma phospholipid DHA content after 4 months of DHA or placebo treatment and final scores on any component (r = 0.103-0.153), or between the change in plasma phospholipid DHA content from baseline to 4 months and change in scores on any component (r = –0.185-0.083) during this period. Mean scores for all behaviors assessed by the parental CBCL (Table IV) tended to decrease from baseline to 4 months, but none of these changes was statistically significant in either group. There were also no statistically significant differences between groups in any of the behaviors assessed after 4 months of DHA supplementation compared with placebo. Further, there were no differences between groups at any time on any behavior measured by
the parental Conners’ Rating Scales (data not shown).
DISCUSSION Epidemiologic data suggest that populations with lower ω3 fatty acid consumption and, hence, lower plasma and, presumably, tissue contents of ω3 fatty acids, including DHA, have higher rates of psychiatric disorders.38 There is a direct relationship between plasma phospholipid DHA content and metabolism of serotonin and dopamine within the central nervous system.39,40 In addition, DHA and other long-chain polyunsaturated fatty acids may influence synaptic function directly through effects on membrane structure, as well as indirectly through the generation of eicosanoids (prostaglandins, leukotrienes, thromboxanes) or through immune system/cytokine interactions. Thus, there 193
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Table IV. Parental CBCL T-scores* at baseline and after 4 months of DHA or placebo treatment
Internalizing behaviors DHA (n = 27) Placebo (n = 26) Externalizing behaviors DHA (n = 27) Placebo (n = 26) Socialization problems DHA (n = 27) Placebo (n = 26) Thought problems DHA (n = 27) Placebo (n = 26) Attention problems DHA (n = 27) Placebo (n = 26)
Baseline
4 Months
58.2 ± 2.4 54.9 ± 2.1
53.1 ± 2.1 51.2 ± 1.5
62.6 ± 2.1 58.5 ± 2.3
58.5 ± 2.1 56.3 ± 2.2
61.5 ± 1.9 58.6 ± 1.6
56.7 ± 1.6 56.3 ± 1.5
60.1 ± 1.9 56.2 ± 1.4
56.8 ± 1.5 56.5 ± 1.5
68.2 ± 2.1 64.3 ± 1.2
64.4 ± 1.9 60.9 ± 1.6
Values are expressed as mean ± SEM. *A T-score >70 indicates a clinically significant behavioral problem.
has been considerable interest in the potential role of long-chain polyunsaturated fatty acids in the etiology and treatment of a variety of psychiatric disorders, such as impulsive violence,40 depression,41 aggression,42 and bipolar disorder,43 as well as ADHD of childhood.22,23,44-46 In two prior studies,45,46 no consistent improvement in behavior of children with ADHD was observed incident to supplementation with evening primrose oil (a concentrated source of 18:3ω6, which can be converted to arachidonic acid (20:4ω6)). However, the effect of supplementation with ω3 long-chain polyunsaturated fatty acids on the symptoms of ADHD has not been studied previously. As observed by others,22,23 the children with ADHD who participated in the study reported here had low levels of plasma phospholipid DHA at baseline and, as expected, supplementation with DHA (345 mg/d) for 4 months increased plasma phospholipid DHA content. However, despite the approximately 2.6-fold increase in plasma phospholipid DHA incident to DHA supplementation, there were no statis194
tically significant differences between groups in any laboratory measure of ADHD symptoms or in any component of two parental behavioral scales after 4 months of DHA supplementation compared with placebo. In fact, errors of omission, a TOVA component that reflects inattention, increased significantly in the DHA group but not in the placebo group, and errors of commission, a TOVA component that reflects impulsivity, decreased significantly in the placebo group but not in the DHA group. The lack of an effect of DHA supplementation on ADHD symptoms does not necessarily mean that a low brain or synaptic content of DHA is not involved in the etiology of ADHD. Because the turnover of fatty acids in the brain is likely to be quite low in 6- to 12-year-old children, a longer period of supplementation and/or a larger amount of supplement might be required to alter the fatty acid content of the central nervous system. It is also possible, as reported for piglets,47 that the plasma phospholipid content of DHA is a poor reflector of brain or synaptic DHA content. In isolated cell systems, α-linolenic acid
(18:3ω3), the obligate precursor of DHA, as well as other desaturated and elongated products of 18:3ω3 are taken up by cerebral microvascular endothelial cells and converted to DHA by astrocytes, which in turn release DHA for uptake by neurons.48-50 If a similar process is involved in vivo, the level of brain DHA could be largely independent of the plasma lipid level of DHA. However, supplementation with fish oil, which contains precursors of DHA, or with α-linolenic acid, which results in higher plasma lipid levels of these precursors, as well as DHA, might be a more effective treatment. The possibility that the amount of DHA in synaptic membranes has no effect on synaptic transmission or that the DHA content of synaptic membranes does not influence the specific neurotransmitter systems involved in the genesis of ADHD must also be considered. In addition, it is important to remember that the plasma phospholipid content of arachidonic acid is also low in children with ADHD and decreases further with DHA supplementation. Thus, any future study of the effect of DHA on ADHD symptoms should include supplementation with both arachidonic acid and DHA. Future studies must evaluate the same or a higher dose of DHA given for a longer period, supplementation with other ω3 fatty acids, and/or supplementation with a combination of ω3 and ω6 fatty acids. The possibility that more optimal DHA intake during early life may decrease the prevalence of ADHD should also be evaluated. However, it is clear from the data presented here that DHA supplementation for 4 months did not ameliorate the symptoms of ADHD. Thus, these data do not support the efficacy of DHA supplementation, as provided in this study, as an alternative or adjunctive treatment for ADHD. We gratefully acknowledge the assistance of C. Boutte, Study Coordinator, the editorial advice of L. Loddeke, and the secretarial expertise of R. Newsom.
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