Platelet and whole blood serotonin content in depressed inpatients: Correlations with acute and life-time psychopathology

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Platelet and Whole Blood Serotonin Content in Depressed Inpatients: Correlations with Acute and Life-Time Psychopathology J. John Mann, P. Anne McBride, George M. Anderson, and Tammy A. Mieczkowski

Platelet or whole blood serotonin content did not differ significantly in patients with major depression compared to healthy controls, but within the patient group, platelet serotonin levels correlated negatively with severity of depression (r = -0.49, p = 0.007). Levels were 39% lower in patients who had made a suicide attempt compared to nonattempter patients (47.2 +_ 27.3 versus 77.6 +- 41.7 ng/lOs platelets, p = 0.04). Conversely, comorbid borderline personality disorder (85.3 +- 41.5 ng/lOs platelets) was associated with 31% greater platelet serotonin content than nonborderline patients (58.9 +- 31.1 ng/lOs platelets) and 27% greater than healthy controls (62.4 +- 19.8 ng/ l Os platelets ). A pronounced seasonal variation in whole blood and platelet serotonin content was found in both patients and controls, largely due to lower levels in summer. Excluding cases tested in the summer abolished the statistically significant differences in patients with and without comorbid borderline personality disorder (BPD ). Neve,'theless, BPD attempters had lower serotonin levels than BPD nonanempters but higher serotonin levels than non-BPD attempters. Current hostility and a life-time history of aggression were positively correlated with platelet serotonin content (r ffi 0.44, p ffi 0.04 and r = 0.41, p ffi 0.06). This study provides evidence for an association between lower platelet serotonin content and depression and suicidal behavior, and association of higher platelet serotonin content and comorbid borderline personality disorder and behavior traits such as aggressivity.

Introduction An association has been described between reduced serotonergic activity and depressive illness (Heninger et al 1984), suicidal behavior (Mann et al 1989a; Mann et al 1989b), and aggressive behavior (Brown et al 1979; Brown et al 1982a; Coccaro et al 1989; Virkkunen et al 1987; Virkkunen et al 1989a; Virkkunen et al 1989b). Neuroendocrine serotonin challenge tests, such as intravenous l-tryptophan (Heninger et al 1984)

Address reprint requests to Dr. J. John Mann, Laboratories of Neutopharmacology, Western Psychiatric Institute and Clinic,

University of Pittsburgh, 3811 O'Hata Street, Pittsburgh, PA., 15213. From the Laboratories of Neumpharmacology (JJM, TAM), Department of Psychiatry, University of Pittsburgh; Department of Psychiatry (PAM). Cornell University Medical College; and Child Study Center (GMA), Yale University School of Medicine. Received September 23, 1991; revised April 3, 1992. © 1992 Socie',y of Biological Psychiatry

0006-3223/92/$05.00

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and oral fenfluramine (Coccaro et al 1989), stimulate a lower prolactin response in depressed patients. Similar results have also been reported regarding lower levels of CSF 5-hydroxyindeacetic acid (5-HIAA), a serotonin metabolite, in depressed patients (Asberg et al 1984). Suicidal or aggressive behavior also appear to be associated with low CSF 5-HIAA (Brown et al 1979; Brown et al 1982a; Brown et al 1982b; Asberg et ai 1986) ~,id a blunted prolactin response to fenfluramine (Coccaro et al 1989). Platelet serotonin content has been employed as an index of presynaptic serotonin function (Stahl 1977; Stahl et al 1982). Decreased whole blood or platelet serotonin content has been reported in patients with depression by some (Sarai and Kayano 1968; Takahashi 1976; Coppen et al 1976; Banki 1978; Born et al 1980; Quan-Bui et al 1984; Quintana 1992) but not all studies (Todrick et al 1960; Wirz-Justice and Piihringer 1978b; Stahl et al 1983; Meltzer et al 1986; Mtick-Seler et al 1991). Because serotonin reuptake inhibitors and 5-HTz receptor antagonists may decrease platelet serotonin content (WirzJustice and P~ihringer et al 1978b; Amstein et al 1988), previous psychotropic drug exposure, in addition to differences in diagnostic criteria, gender ratio, severity and subtypes of depression may have contributed to the discrepancies between these studies. Another factor that results in large variations in platelet serotonin content is seasonal variation (Wirz-Justice and Piihringer 1978a) and this has not been controlled for in most studies. The relaticnship between platelet serotonin content, aggressivity, and suicidality also warrants study bccause suicidal and aggressive behavior are associated with lower levels of CSF 5-HIAA (Asberg et al 1984; Asberg et al 1986; Virkkunen et al 1987; Virkkunen et al 1989a; Virkkunen et al 1989b) and a blunted prolactin response to the serotonin agonist fenfluramine (Coccaro et al 1989). Reduced serotonin levels have been reported by one study in suicidal female schizophrenics compared to nonsvicidal female schizophrenics or controls (Braunig et al 1989), but no differences in blood serotonin levels were lbund in suicide attempters versus nonattempters in another study (Meltzer and Arora 1986) that included a variety of diagnostic groups including depression and schizophrenia. In the present study, we have concurrently examined the relationship of suicidal behavior, depression, aggressivity, and season to whole blood and platelet serotonin content in drug-free depressed inpatients. Methods We studied 29 patients and 27 normal controls. Patients admitted to an acute care, private psychiatric hospital and meeting DSM-III-R criteria for a major depressive episode (Spitzer et al 1989) were admitted to the study. All patients and controls gave written informed consent as required by the Institutional Review Board. All patients and controls were off psychotropic drugs or drugs known to affect monoamines for at least 2 weeks prior to study. Chloral hydrate was permitted for distressing insomnia but was rarely used. The minimum drug-free period was 6 weeks in the case of fluoxetine and 1 month for oral antipsychotic medication. The mean drug-free period was 149.7 _ 163.2 days. The range of the drug-free period was recorded as 14 to 365 days because the maximum drug-free period was designated as 365 days. in the group of 12 recent suicide attempters, the mean time between suicide attempt and biological testing was 13.8 _ 12.3 days. Table 1 describes the clinical and demographic characteristics of the patients and control subjects. The patients had been recently hospitalized for evaluation and treatment of depression, and were studied prior to initiation of treatment. All were free from

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Table 1. Demographic and Clinical Variables in Depressed Patients and Normal Controls Depressed patients Number of Subjects Age (years) Sex (% Female) Age of onset of depression (years) History of depression in a first degree relative (%) Hamilton Depression Scale score, (24-item version) Hamilton Anxiety Scale Score GAS Score Unipolar (%) Bipolar (%) MelanchoLia (%) Psychotic Features (%) Recent Suicide Attempt (%) Concurrent diagnosis of Borderline Personality Disorder (%) Drug-Free Interval (days) "Depressed patients versus controls

t =

29 42.5 ~ ± 13.9 75.9 31.1 ± 15.8 27.6 31.2 ± 7.8 33.4 ± 10.3

Controlsubjects 27 35.6 ± 12.6 55.6

41.6 ± 9.8 86.2/13.8 62.1 13.8 41.4 27.6 149.7 --. 163.2

- 1.94, d f ffi 54, p ffi 0 . 0 6 .

significant or active physical illness on the basis of physical examination and routine laboratory tests. The diagnosis of a major depressive episode (MDE) was generated by two research psychiatrists according to DSM-III-R criteria. Most patients had a major depressive (unipolar) disorder (86%), without psychotic features (86%). Almost twothirds of the patients (62%) met criteria for melancholia. The level of depression was moderately severe as indicated by a mean Hamilton Depression Scale (Hamilton 1960) score of 31.0 and the fact that 41% had made a recent suicide attempt. A categorical diagnosis of Borderline Personality Disorder (BPD) was made using a DSM-III-R checklist and the severity of BPD assessed using the Schedule for Interviewing Borderlines (SIB; Baron et al 1980). The percentage of patients who qualified for a diagnosis of BPD was 27.6%. In 22 of the 29 patients, general psychopathology was assessed using the Brief Psychiatric Rating Scale (BPRS) developed by Overall and Gorham (1962). Lifetime history of aggression was rated using the Brown-Goodwin Assessment for History of Lifetime Aggression (Brown et al 1979). Sensation-seeking behavior was assessed by the Zuckerman Interest and Preference Scale (Zuckerman 1971; Zuckerman 1978). Suicidal behavior was assessed by the Medical Damage or Lethality Scale (Beck et al 1975) and by the Suicide Intent Scale (Beck et al 1975). The method of suicide attempts included overdose of medications (n = 7), cutting self (n = 3), burning self (n = 1), and attempted hanging (n = 1). Controls were healthy adults recruited by advertisements or word of mouth from medical center staff and the neighborhood. All were free from physical and mental illness on the basis of a screening interview. All were totally drug-free including aspirin and other nonsteroidal anti-inflammatory drugs, for at least 2 weeks prior to testing. Blood samples were drawn between 8 and 9 AM into a glass Vacutainer tube (Becton Dickinson Vacutainer Systems, Rutherford, N J) containing EDTA as the anticoagulant, and a whole blood platelet count obtained. Ascorbic acid (50 ttl, 25%) and an internal standard, 5-HTP (100 ng), were added to 250 ttl of whole blood. Subsequently, 50 p,l of perchloric acid (3.5 tool/L) were added and the samples were vortexed for 10 sec and placed on ice for 10 min. The samples were then centrifuged at 10,000 g for 5 rain and the supernatant stored at -70°C untill shipped in dry ice to Yale University (GMA) for

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Table 2. Comparison of Whole Blood and Platelet Serotonin Content in Depressed Subjects Versus Normal Controls (ng/rnl and ng/10 8 platelets; mean -+ SD)

All subjects Platelet Whole Blood Males Platelet Whole Blood Females Platelet Whole Blood

Depressed (n)

Controls (n)

t

64.7 .4- 36.4 (29) 169,5 __ 74.5 (29)

62.4 ± 19.8 (25) 153.1 - 48.3 (27)

0.27 0.97

62,1 ± 29.0 (7) 159.9 -- 76.2 (7)

64.1 ± 22.9 (11) 144.7 ± 53.5 (12)

-0.16 0.51

65.5 ± 39,0 (14) 172.5 -*--75,5 (22)

61,2 ± 17.8 (14) 159.7 "*" 44.5 (15)

0.39 0.59

F 3.37 c 2.38 b !.59 2.03 4.82 c 2.88 t'

Patients versus controls:~p < 0.1; bp < 0,05; Cp < 0.01,

assay. Whole blood serotonin content was assayed by HPLC using our previously published method (Anderson et al 1987). The detection limit of the assay in less than 1 ng/ml and the day-to-day coefficient of variance (cv) for samples is 7.2%. The within-day cv is 3-5%. Because almost all serotonin in whole blood is located in cytoplasmic storage granules within the platelet (Sneddon 1973), results are expressed as platelet serotonin content (ng/10s platelets) as well as whole blood serotonin content (ng/ml ~hole blood). Group comparisons were performed using one-way and two-way analysis of variance. T-tests were used when only two groups were being compared. Pearson Product Moment Correlation coefficients were calculated to test for linear relationships between two variables. Whole blood serotonin content and platelet serotonin content were both normally distributed. The Kolmogorov-Smirnov statistic revealed no significant departures from normality for either of these variables. All data are reported as mean +_ standard deviation unless otherwise stated. Results

Comparison of Serotonin Content in Depressed Subjects Versus Normal Controls Mean whole blood serotonin content did not differ significantly between depressed subjects and normal controls in either the total pool of subjects or within subgroups defined by gender (see Table 2). However, there was a trend for platelet number to be higher in patients versus controls (2.9 _ 0.8 x 10S/ml versus 2.5 - 0.5 x 10e/ml, respectively; t = 1.87, df = 52, p = 0.07). This effect was significant in depressed males versus healthy male controls (2.6 _ 0.2 x 10S/ml versus 2.2 4._ 0.4 x 10~/ml; t = 2.5, df = 16, p = 0.02) and nonsignificant in female depressives versus female controis (2.9 _ 0.9 x 10S/ml versus 2.7 _ 0.6 x 10S/ml, t = 0.74, df = 34, p = 0.5). When mean whole blood serotonin content was corrected for platelet number, there was no significant difference in platelet serotonin content between depressed subjects and normal controls (see Table 2). Although mean whole blood and platelet serotonin content did not differ significantly between depressed subjects and normal controls, levels were significantly more variable in the depressed group compared to the control group (mean whole blood: F = 2.38, df = 28,26, p = 0.3; mean platelet serotonin content: F = 3.37, df =

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28,24, p = 0.003). In analyses by gender, whole blood and platelet serotonin levels were significantly more variable in the female depressed groups compared to female controls (F -- 2.88, df = 21,14, p = 0.05 and F - 4.82~ df = 21,13, p = 0.005, respectively) but not in male patients compared to male controls (F = 2.03, df ~6,11, p - 0.3 and F -- 1.59, df = 6,10, p - 0.5, respectively; see Table 2). Further analyses were done to explore other possible causes for the greater variability within the depressed group.

Effects of Season of Year on Whole Blood and Platelet Serotonin Content To test for the effects of season, subjects were divided according to the date of biological testing into four categories: Mmch 21-June 21, June 21-September 21, September 21-December 21, and December 21-March 21. The groups were labeled spring, summer, fall, and winter, respectively. A two-way analysis of variance was performed to test if the variance in whole blood or platelet serotonin content could be explained by season, group membership (depressed versus control), or by an interaction of the two. A significant main effect for season was found for whole blood serotonin (F = 5.97, (if = 3,20, p - 0.004) and platelet serotonin content (F = 7.08, at -- 3,45, p - 0.001). Mean values of whole blood serotonin content were: spring 180.2 ± 60.6 (n -- 8), summer 107.6 __ 45.8 in - 14.), fall 178.4 -+ 63.3 (n = 10), and winter 183.0 _+ 56.8 (n = 23). Mean values of platelet serotonin content were: spring 73.6 -+ 24.4 in - 8), summer 39.9 _+ 20.2 (n -- 14), fall 71.8 -+ 21.2 in = 8), and winter 72.8 -- 31.8 in - 23). Thus, the main effect was largely due to the finding of lower levels in summer relative to the other seasons. However, there was no significant group effect or interaction effect.

Relationship Between Demographic and Clinical Variables and Whole Blood and Platelet Serotonin Content Effects of ABe and Gender. Whole blood serotonin content and age were not significantly correlated in the deplessed group (r -- 0.12, n - 29, p -- 0.55), or in the control group (r - 0.15, n = 27, p - 0.46). Similarly, platelet serotonin content and age were not significantly correlated (depressed subjects: r - 0.06, n -- 29, p = 0.75; control subjects: r -- - 0 . 0 4 , n - 25, p - 0.84). Values for whole blood serotonin content did not significantly differ between males and females in depressed subjects (159.9 __- 76.2 versus 172.5 --- 75.5 ng/ml, respectively; df = 27, t - - 0 . 3 8 , p = 0.70); normal controls (144.7 _ 53.5 versus 159.7 +_ 44.5 ng/ml, respectively; df - 25, t - - 0 . 8 0 , p -- 0.43); or in the combined group of depressed subjects and normal controls (150.3 -+ 61.2 versus 167.4 - 64.3 ng/ml; (If - 54, t = - 0 . 9 5 , p = 0.35). Values for platelet serotonin content did not differ significantly between males and females (depressed subjects: 62. I -29.0 versus 65.5 - 39.0, t -- - 0 . 2 1 , df = 27, p = 0.8; control subjects: 64.1 _ 22.9 versus 61.2 -+ 17.8, t = 0.36, df -- 23, p = 0.73; all subjects: 63.3 _+ 24.6 versus 63.8 __. 32.2, t = - 0 . 0 6 , df = 52, p = 0.95). Relationshipto DepressiveSubtype. Patients were assigned to the following categories: major depressive episode (MDE) with psychotic features; MDE with melancholia but without psychotic features; and MDE without psychotic features or melancholia. A oneway analysis of variance was performed, including the above subtypes and the normal

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Table 3. Whole Blood and Platelet Serotonin Content in Major Depression Episode (MDE): Effect of Subtypes of MDE, Psychotic Features, Borderline Personality Disorder or Suicidal Behavior

Group I. Subtypeof Depression MDE with Psychotic features MDE with melancholia without psychotic features MDE without melancholia or psychotic features 2. Comorbid Dorderline Personality Disorder MDE with Borderline personality Disorder (BPD) MDE without BPD 3. Recentsuicide attempt MDE & Suicide attempter (within 2 months) MDE & Suicide nonattempter (lifetime)

Whole blood serotonin content (ng/ml) Mean _+ SD (n)

Platelet serotonin content (ng/10s platelets)

138.5 -+ 118.0 (4)

48.4 +_ 37.9 (4)

170.5 -+ 60.4 (15)

65.7 ± 26.6 (15)

180.4 ± 80.0 (10)

69.6 ± 49.0 (IO)

214.7~ ± 40,8 (8)

58.9° ± 31.1 (20)

157.6 ± 75.9 (20)

85.3 ± 41.5 (8)

143,8 .4- 81,3 (12)

47.2b ± 27.3 02)

190,3 - 72.5 (14)

77.6 ± 41.7 04)

Op< 0.10; bp < 0.05.

control group. No significant main effects were found either when whole blood serotonin content (F = 0.72, df = 3,52, p = 0.5) or platelet serotonin content (F - 0.51, df = 3,50, p = 0.7) were analyzed (see Table 3). A second contrast was carried out, confined to patients having MDE with melancholia, MDE without melancholia, and normal controls, and again indicated no significant group differences (whole blood serotonin content: F = 0.46, df = 2,53, p = 0.6; platelet serotonin content: F = 0.04, df = 2,51, p = 0.96).

Relationship to Symptom Severity. Platelet serotonin content correlated negatively with the 24-item Hamilton Depression Scale total score, but not with the subscores (see Table 4). Whole blood serotonin content did not correlate significantly with scores from the Hamilton Depression Scale, although a trend (p = 0.08) for a negative correlation was also observed. Neither whole blood nor platelet serotonin content were correlated with the Hamilton Anxiety Scale score, There was a significant positive correlation of the Global Assessment Scale (GAS) score with whole blood serotonin content and with platelet serotonin content (see Table 4),

Reiationship to the Presence or Absence of Borderline Personality Disorder. Mean values of whole blood serotonin content were compared in depressed patients with and without coexistent Borderline Personality Disorder (BPD; see Table 3). The mean whole blood serotonin content appeared higher in the BPD patients compared to patients without this diagnosis (214.7 _ 40.8 versus 157.6 _ 75.9 ng/ml, respectively, t = 2.00, df = 26, p = 0.06), and compared to normal controls (214.7 +_ 40.8 versus 153.1 _ 48.3 ng/ml, t = - 3 . 3 , df = 33, p = 0.003). Of the non-BPD patients, 6 of 19 were tested in the summer as opposed to 1 of 8 BPD patients, which may have accounted for the lower lev-

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Table 4. Correlations Between Whole Blood and Platelet Serotonin Content and Scores on Scales Measuring Symptom Severity Whole blood serotonin content

Hamilton Depression Scale 24-item Total Psychomotor Agitation Subscale Score Psychomotor Retardation Subscalc Score Hamilton Anxiety Scale Global Assessment Scale

Platelet semtonin content

r

n

r

n

-0.33 a - 0.25 -0.18 0.08 0.49 c

29 29 29 22 29

-0.49 ~ - 0.25 -0.19 0.03 0.24 c

29 29 29 22 29

'*p < 0.10

~p < 0.05 ~p < O.OI

els of serotonin in the non-BPD group. To test this possibility, the above analysis was recomputed excluding subjects that were tested in the summer. Although the BPD group had a higher mean whole blood serotonin content (216.7 _+ 43.6) than those patients without this diagnosis (195.7 _+ 63.8), after excluding the cases tested in the summer the difference was no longer statistically significant (t ffi - 0.78, df = 18, p = 0.4). However, the difference between patients with BPD and healthy controls remained significant (216.7 __ 43.6versus 160.7 _+ 51.2, t = - 2 . 5 9 , df = 2 6 , p = 0.02). Platelet number expressed as l0 s platelets/ml did not differ significantly in the above groups (BPD patients, 2.9 - 0.95 versus patients without this diagnosis, 2.9 -+ 0.7, t = 0.06, df ffi 26, p = 0.96; and versus controls 2.5 - 0.5, t = - 1 . 1 8 , df = 31, p = 0.25). There was a trend for the BPD group to have higher platelet serotonin content than the non-BPD group (85.3 _+ 41.5 versus 58.9 -+ 31.1, t = - 1.84, df - 26, p = 0.08) and significantly higher platelet serotonin content versus controls (62.4 -+ 19.8, t 2 . 1 4 , df = 31, p = 0.04; see Table 3). When patients tested during the summer were excluded from the analysis (6 of 19 non-BPD patients, 1 of 8 BPD patients), the patients with BPD no longer had statistically significant higher mean platelet serotonin content (87.12 - 44.47) compared to those without BPD (75.09 4- 25.73; t = - 0 . 7 7 , df = 18, p = 0.4). Similarly, after excluding the cases tested during the summer (1 of 8 BPD patients and 6 of 27 controls), there was only a trend for those with BPD to have a higher mean platelet serotonin than the healthy controls (87.12 -+ 44.47 versus 65.78.4- 20.28, t-

-l.70,

df=

24, p = 0 . 1 0 ) .

The mean whole blood serotonin content in depressed patients without coexistent Borderline Personality Disorder did not differ significantly from normal controls (157.6 _+ 75.9 versus 153.1 +- 48.3 ng/ml, t -- 0.25, df = 45, p = 0.8) but the variance of the depressed group was significantly larger than the normal controls (F = 2.47, df 19,26, p = 0.03). The increased variance in the patient group was stiil present at~er adjusting for platelet number, but was no longer present when the analysis was done excluding the summer cases. The Schedule for Interviewing Borderlines (SIB) total score assessed severity of BPD and was available for 20 of the 29 patients. The SIB score was positively correlated with whole blood serotonin levels, btlt the result was not statistically significant (r = 0.24, n = 20, p = 0.3).

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Relationship to Suicidal Behavior. Platelet serotonin content was significantly lower in depressed patients who had recently auempted suicide (within the previous 2 months) compared to patients who had never a~empted suicide (47.2 ± 27.3 versus 77.6 -.- 41.7 ng/108 platelets, t = 2.16, df = 24, p = 0.04). Although mean whole blood serotonin content appeared lower in recent suicide attempters compared to patients without a history of a suicide attempt, the difference was not statistically significant (143.8 _+ 81.3 versus 190.3 - 72.5 ng/ml, t = 1.54, df = 24, p = 0.14). Because 6 of the 12 recent attempters and only 2 of the 13 nonattempters were tested during the summer, additional analyses were performed excluding these cases. Comparison of whole blood and platelet serotonin content in recent attempters versus life-time nonattempters suggested lower levels in attempters, but the difference in the means did not reach statistical significance for whole blood serotonin content (190.43 -+ 76.22 versus 217.45 ± 52,29, t = 0.87, df = 15, p = 0.4), or platelet serotonin content (61.35 - 26.23 versus 90.58 ± 36.85, t = 1.71, df = 15, p = 0.11). Among the recent suicide attempters, there was no correlation between whole blood or platelet serotonin content and medical damage or lethality of the suicide attempt rated using the Medical Lethality Scale (r - 0.19, n -- 12, p = 0.6; r - - 0 . 0 4 , n - 12, p = 0.9). There was also no correlation between whole blood or platelet serotonin content and an overall objective rating of suicidal planning behavior as derived by a factor analysis of the Suicide Intent Scale (r = 0.19, n = 12, p = 0.6; r = 0.01, n = 12, p = 0.97, respectively). Platelet number was not related to either the medical lethality nor degree of planning behavior. There was no difference in platelet count in attempters as comp~a'ed to nonattempters (3.16 ± 0.84 × 108 platelets/ml versus 2.68 ± 0.71 × 108 platelets/ml, t = 1.57, df = 24, p = 0.13). When recent suicide attempters with a concurrent diagnosis of BPD were compared to those who had a diagnosis of BPD but never attempted suicide, there was a trend for the suicide attempters with BPD to have lower whole blood serotonin content (211.3 17.6 versus 263.5 ± 46.0, t = 2.19, df - 4, p -- 0.09) and lower platelet serotonin content (65.75 ± 19.9 versus 137.8 ± 58.8, t = 2.44, df = 4, p - 0.07). When patients with BPD and a life.time history of a suicide attempt were compared to those with BPD and no life-time history of suicide attempt, there was a significant difference in whole blood serotonin content (198.4 ± 25.1 versus 263.5 ± 46.0, t - 2.69, df 6 , p - 0.04) and platelet serotonin content (67.78 ± 15.8 versus 137.8 4. 58.8, t = 3.07, df -- 6, p = 0.02). Even excluding those subjects tested during the summer, the above results remained the same. When BPD attempters were compared to non-BPD attempters, the BPD attempter group had significantly higher whole blood serotonin content than the non-BPD attempter group (198.37 ± 25.12 versus 117.94 _ 78.28, ': = 2.41, df = 13, p = 0.03). There was also a trend for platelet serotonin content to be higher in BPD attempters compared to non-BPD attempters (67.78 ± 15.75 versus 42.36 ± 28.20, t = 1,99, df = 13, p = 0.07). Because 5 of the 9 non-BPD attempters and only 1 of the 6 BPD attempters were tested during the summer, another analysis was performed excluding all of those tested during the summer. Although the BPD attempters had higher whole blood and platelet serotonin content, the results were no longer statistically significant (whole blood serotonin content: 198.04 ± 28.08 versus 169.78 ± 91.0, t = 0.67, df = 7, p = 0.53; platelet serotonin content: 66.85 ± 17.42 versus 63.87 ± 29.15, t = 0.19, df = 7, p - 0.85). Two-way analysis of variance was performed to simultaneously test for main effects and an interaction between a BPD diagnoses and lifetime suicide attempt history. Sig-

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Table 5. Correlations Between Whole Blood and Platelet Serotonin Content and Scores on Scales Measuring Aggressivity and Impulsivity

BPRS Total Anxiety and Depression Anergia Thought disorder Activity disturbance Hostility Aggression History Scale (n = 21) Total Zuckerman Sensation Seeking Total Thrill and Adventure Experience Seeking Disinhibiton Boredom Susceptibility

Whole blood serotonin (ng/ml) (n = 22)

Platelet serotonin content (rig/10 s platelets) (n = 22)

r

r

-0.06 0.02 -0.36 a - 0.32 -0.02 0.44 b

-0.15 -0.24 -0.43 b - 0.25 -0.09 0.41 a

0.4P 0.12 0.03 0.22 - 0.004 0.08

0.42 a 0.28 0.13 0.38 0. ! 7 0.09

"p <0.10 bp < 0.05 ~p < 0.0l

nificant main effects were found for whole blood serotonin content (BPD: F = 8.73, df = 1,24, p = 0.007; suicide attempt: F = 8.66, df = 1,24, p = 0.007), and for platelet serotonin content (BPD: F = 9.96, df = 1,24, p = 0.004; suicide attempt: F = 12.94, df = 1,24, p = 0.001). No significant interactions were found (F = 0.02, df = 1,24, p = 0.90; F = 2.37, df = 1,24, p = 0.14, respectively). When the above analysis was recomputed excluding those subjects tested during the summer, the results were no longer statistically significant for whole blood serotonin content (BPD: F = 1.98, d f = 1,16, p = 0.18, suicide attempter: F = 2.96, df = 1,16, p = 0.11; interaction: F = 0.24, df -- 1,16, p = 0.63). With regard to platelet serotonin content, there was a significant main effect for attempter status (F - 6.86, dt = 1,16, p = 0.02) and a trend for a BPD main effect (F = 3.57, d f = 1,16, p = 0.08) and an interaction effect (F = 3.81, df = 1,16, p = 0.07).

Relationship to Clinical Variables Measuring Impulsivity and Aggression. Whole blood serotonin content was significantly correlated with the Brief Psychiatric Rating Scale (BPRS) subscale score for hostility (r = 0.44, n = 22, p = 0.04) as defined by the five-factor varimax solution o f Guy, Cieary, and Bonato (1976). Platelet serotonin content was also correlated with this subscale score but it only approached significance (r = 0.41, n = 22, p = 0.06). Neither whole blood or platelet serotonin content were correlated with the remaining BPRS subscale scores (see Table 5). Whole blood and platelet serotonin content correlated positively with the total score of the Brown-Goodwin Aggression History Scale total score (r = 0.41, n = 21, p = 0.06 and r = 0.42, n = 21, p = 0.06, respectively) but only at a trend level of significance. No significant correlations were found with the Zuckerman Sensation Seeking Scale subscores (see Table 5).

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Relationship to the Duration of the Drug-Free Interval. Values for whole blood serotonin content or platelet serotonin content did not correlate with the duration of the drug-free interval prior to study (r = 0.03, n = 29, p = 0.87; r = 0.10, n -- 29, p = 0.6, respectively). Furthermore, there was no significant difference in the mean whole blood and platelet serotonin content of those patients who were drug-free for 6 weeks or less versus those drug-free for more than 6 weeks (t = - 0 . 3 3 , df = 27, p = 0.7, and t = - 0 . 7 7 , df = 27, p = 0.45, respectively).

Discussion We did not find a difference in mean whole blood or platelet serotonin content in the depressed patient group compared to healthy controls. However, both the severity of depression and global psychiatric impairment correlated negatively with platelet serotonin content. The variance in platelet serotonin was significantly greater in the depressed patients than in the controls, suggesting that some factor other than a categorical diagnosis may influence whole blood or platelet serotonin content. Seven previous studies had found lower whole blood or platelet serotonin levels in depressed adults compared to healthy controls (Sarai and Kayano 1968; Takahashi 1976; Coppen et al 1976; Banki 1978; Born et al 1980; Quan-Bui et al 1984; Quintana 1992). Another study found lower blood ~erotonin content in boys with MDD compared to boys with schizophrenia or schizotypal disorder but not compared to healthy controls (Rogeness et al 1985). Several studies found no difference in platelet serotonin content in patients with unipolar major depression compared to controls (Todrick et al 1960; Wirz-Justice and Piihringer 1978a; Stahl et al 1983; Meltzer and Arora 1986; Miick-Seler et al 199 I). In those adult studies that reported lower blood serotonin levels in depressed natients compared to healthy controls (Sarai and Kayano 1968; Takahashi, 1976; Coppen et al 1976; Banki, 1978; Born et al 1980; Quan-Bui et al 1984; Quintana, 1992), there was no difference in the variance between the groups, suggesting that a more homogeneous patient type may have been included in these studies. It is also possible that these studies included a higher proportion of more severely depressed patients without BPD than the studies that failed to find lower levels compared to controls. Subtype of depression may be relevant because it has been reported that bipolar patients have higher platelet serotonin content than unipolar patients or controls (Wirz-Justice and P0hringer 1978a; Stahl et al 1983) and that this alteration is stateindependent (Wirz-Justicc and Ptihringer 1978a). However, other investigators did not confirm this finding (Takahashi 1976; Born et al 1980). Another potential confound is tricyclic antidepressant treatment because serotonin reuptake inhibitors lower platelet serotonin content (Wirz-Justice ~.nd Piihringer 1978b; Corona et al 1982; Stahl et al 1983). In several studies (Quan-Bui et al 1984; Mtick-Seler et al 1991), a significant proportion of the patients were not drug-free at time of study or had a short drug-free period, such as 7 days (Takahashi 1976; Miick-Seler et al 1991). With regard to psychotic depression, we were not able to confirm the report by MtickSeler et al (1991) that psychotic depression was associated with higher platelet serotonin content than nonpsychotic depression and that whole blood serotonin was high in psychotic depression relative to controls (Todrick et al 1960). It is noteworthy that the drug-free interval in the study by Miick-Seler et al (1991) was only 7 days and that antidepressants and antipsychotics may alter platelet serotonin content, thereby potentially accounting for the differences in results. In agreement with our findings, other investigators have not found age to be correlated

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with whole blood serotonin (Coppen et al 1976; Stahl et al 1983; Quan-Bui et al 1984). In contrast to our findings, Coppen et al (1976) and Quan-Bui et al (1984) reported higher whole serotonin levels in normal females compared to males. In agreement with our results, Coppen et al (1976) and Stahl et al (1983) found no gender differences in depressed patients. Todrick et al (1960) reported a significant menstrual effect, which may also account for some of the disagreement in the literature. In the present study, analyses were performed to identify factors in addition to depression that may influence platelet serotonin content. Season, presence of a history of a suicide attempt, aggressive traits, or current behavior and comorbid BPD were found to correlate with platelet serotonin content. Several factors were ruled out in our study, including age, gender, subtype of depression, psychomotor agitation or retardation, anxiety, and residual drug effects. We found a significant seasonal variation in platelet and whole blood serotonin content in both healthy controls and depressed patients. The levels in the summer were lower than the other seasons. A previous report (Wirz-Justice and Piihringer 1978a) found that platelet serotonin was highest in the late autumn and spring. In addition, they found diurnal effects with 8 AM levels higher than 4 PM levels in controls in the first 6 months of the year and the reverse in unipolar depressives. We avoided diurnal effects by testing all subject at about 8:30 AM. Our findings highlight the importance of controlling for seasonal effects because drag-free depressed inpatients are often difficult to find and such studies generally extend over several seasons or years. Seasonal effects are not confined to platelet and whole blood serotonin but have also been reported for brain levels of 5hydroxyindoleacetic acid (Carlsson et al 1980). The seasonal variation in ~ates of suicide and depressive illness may be related to seasonal fluctuations in serotonin system function. A relationship was found between higher serotonin content and a diagnosis of comorbid BPD. A weak trend was found for severity of BPD to correlate positively with whole blood serotonin content. A lifetime history of MDE is found in most cases of BPD (Friedman et al 1982); and as seen in this study, about one quarter of the patients presenting with MDE had comorbid BPD. The depressed patients with comorbid BPD had elevated platelet serotonin content and a similar trend for whole blood serotonin levels compared to healthy controls. Depressed patients without comorbid BPD did not differ from healthy controls and had intermediate levels with respect to BPD cases. Although excluding cases studied in the summer appeared to eliminate the statistical significance of this effect, the difference may prove significant once a larger sample of patients is studied. What also cannot be determined at this point is whether the elevation in whole blood serotonin is present in nondepressed patients with BPD. The group of depressed patients without BPD had significantly more variable whole blood serotonin content than patients with BPD (F = 4.36) or the control group (F ffi 2.73, df = 27,26, p = 0.01), indicating that the presence of comorbid BPD in the MDE population defined a biologically more homogeneous group. Clearly, axis II diagnoses may contribute to the variance in serotonin levels in depressed patients and future studies should include such assessments. A relationship between altered serotonin function and suicidal behavior has been suggested based on studies of serotonin levels and receptors in the brain of suicide completers (Mann et al 1989a) and CSF 5-HIAA in suicide attempters (.~sberg et al 1976). We assessed this relationship by treating suicidal behavior both as a categorical variable (patie~ts who had made a suicide attempt within 2 months of study versus those who had never made a suicide attempt) as well as continuous variable involving the dimensions of medical damage or level of suicide intent or planning. We found lower

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platelet serotonin levels in suicide attempters compared to nonattempters. After excluding cases studied during the summer, this difference remained significant for platelet serotonin content but became significant only at a trend level for whole blood content (p = 0.11). Clearly, the exclusion of such cases reduces statistical power, and additional subjects should be studied to address this point. Brannig et al (1989) found lower blood serotonin levels in suicidal female schizophrenics compared to nonsuicidal female schizophrenics or healthy women. Their definition of "suicidal" was based on a combination of suicidal ideation, a variety of psychopathology, impulsive aggression, or a previous suicide attempt. Thus, it is not clear in their study which component of this range of behaviors or symptoms explained the lower blood serotonin level in the "suicidal" group. Meltzer and Arora 1986 did not find a difference in platelet serotonin content between suicide attempters and nonattempters. They also did not find any difference between violent and nonviolent suicide attempters. They determined suicidality retrospectively based on the item in the Hamilton Depression Scale. Unlike previous studies, we also assessed the degree of lethal intent, suicide planning, and medical damage and found no relationship to serotonin levels. Whole blood or platelet serotonin levels were elevated in depressed patients with comorbid BPD and yet may be reduced in suicide attempters. Because BPD is a condition with a high rate of suicide attempts it may appear that these biological findings are at variance. In a preliminary effort to address this point (based on relatively few subjects per cell), we found that BPD attempters appeared to have higher serotonin levels than non-BPD attempters (not statistically significant when summer cases were excluded but the number of cases was reduced substantially). Moreover, BPD attempters (lifetime history) had significantly lower platelet content than BPD nonattempters. A two-way ANOVA suggests that BPD is associated with increased whole blood and platelet serotonin content, and suicidal behavior is independently associated with reduced serotonin levels, based on the fact that there were significant main effects for both BPD and attempt status, and no significant interaction effects. It is also possible that schizophrenia may be associated with increased platelet serotonin content (Garelis et al 1975; DeLisi et al 1981; Freedman et al 1981; Jackman et ai 1983; Stahl et al 1983; Quan-Bui et al 1984 Rogeness et al 1985; Mtick-Seler et al 1991), although neuroleptics may also affect serotonin content (Joseph et ai 1977; Anderson et al 1987). Thus, the diagnostic composition of the study population may be critical in determining the results. A positive correlation was found between whole blood serotonin content and life-time history of aggression as assessed by the Brown-Goodwin Scale as well as the hostility subscale of the BPRS, which assessed psychopathology at the time of testing. This finding is consistent with the report by Pliszka et al (1988) of a trend for higher blood serotonin in violent juvenile offenders. Raleigh et al (1984) have reported elevated whole blood serotonin in dominant male adult vervet monkeys. This effect was state-dependent because when the same monkeys were not in the dominant position, their serotonin levels fell. Our findings suggested a correlation of serotonin levels with both life-time history of aggression as well as with current level of hostility, suggesting it reflects a stable behavioral trait. The finding of elevated platelet serotonin in association with aggressive behavior indicates another behavioral correlate to be considered in determining the relationship of platelet serotonin to neuropsychiatric syndromes. Aggressivity, particularly impulsive and recurrent aggression, has been found to correlate with reduced CSF 5-HIAA (Brown et

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al 1979; Brown et al 1982a; Virkkunen et al 1987; Virkkunen et al 1989a; Virkkunen et al 1989b) and with a blunted prolactin response to the indirect serotonin agonist, fenfluramine (Coccaro et al 1989). These studies suggest there may be reduced serotonergic activity and therefore increased plateiet serotonin content may reflect impaired release of serotonin, thereby resulting in reduced serotonergic transmission. Alternatively, increased platelet serotonin levels may be an index of altered serotonin function secondary to changes in peripheral tryptophan availability and metabolism. Because it has been reported (Yuwiler et al 1981) that blood serotonin levels can be stable in men for years, it is conceivable that this biochemical index could be a stable biological trait that correlates with a behavioral trait such as aggressivity, or a personality disorder such as borderline personality disorder. The association of increased or decreased platelet serotonin with various neuropsychiatric disorders as well as behavioral traits or states suggests that elucidation of the basis for these biochemical changes may shed light on altered brain serotonin function', which in turn forms part of the pathogenesis of these conditions. This study has provided further evidence for an association between the serotonin system and aggressivity, depression, suicidal behavior, and the Borderline Personality disorder. This work was supported by MH46745, MH40695 and MH37907, and the Research Network on Mental Health and the Law of the John D. and Catherine T. MacArthur Foundation. The technical assistance of Amy Wiley, Esther Nimchinsky, and Jodi Marinacci is much appreciated. The manuscript was expertly typed by Ms. Jean Williams.

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