Excessive water drinking behavior in autism

Brain & Development 21 (1999) 103–106

Original article

Excessive water drinking behavior in autism Katsuyuki Terai a ,*, Toshio Munesue b , c, Michio Hiratani d a

Noto Second Hospital (Division of Neuropsychiatry), 55 Fujihashi-machi, Nanao, Ishikawa, 926-0816, Japan b Fukui Prefectural Mental Health Center, Fukui 910-0846, Japan c Department of Neuropsychiatry, Kanazawa University School of Medicine, Kanazawa, Ishikawa 920-8640, Japan d The Center of Developmental Medicine and Education for Handicapped Children in Fukui Prefecture, Fukui 910-0846, Japan Received 9 November 1997; revised version received 5 October 1998; accepted 8 October 1998

Abstract The aim of this study was to determine the incidence of polydipsia in 49 autistic children, and also the influence of psychotropic drugs and residential factors on water drinking behavior, as compared with in 89 mentally retarded children, in schools for mentally handicapped children in Fukui prefecture. Questionnaires were used to detect polydipsia and to assess the severity of the water drinking behavior in the autistic children and mentally retarded children. The incidence of polydipsia in the autistic children tended to be higher (P = 0.074) than that in the retarded children. The severity of water drinking behavior was significantly higher in autism (P = 0.022) than in mental retardation. The majority of the autistic children with polydipsia had been taking no psychotropic drugs. The incidence of polydipsia showed no significant difference between two residential situations, i.e. ‘not at home’ and ‘at home’. The present study suggests that polydipsia or excessive water drinking behavior occurs more often in autism than in mental retardation, possibly due to some intrinsic factor in autism itself.  1999 Elsevier Science B.V. All rights reserved. Keywords: Water drinking behavior; Polydipsia; Autism; Mental retardation; Residential factor

1. Introduction Excessive water drinking, or polydipsia, is fairly common in children with developmental disorders. A few studies have focused on this behavior in the mentally handicapped, but none in autism. Psychotropic drugs are known to cause water intoxication in patients with schizophrenia, depression, epilepsy and other disorders [1–5]. Therefore, it seemed important to determine whether the polydipsia in autism is due to psychotropic drugs or not. It has been suggested that mentally handicapped individuals have a tendency to drink too much water in closed environments such as institutions for the mentally handicapped [6]. The living situations of Japanese children in schools for the mentally handicapped differ: some children live in institutions for the mentally handicapped or residential facilities attached to schools, whereas others live with their families. The purpose of this study was to determine * Corresponding author. Fax: +81-767-526-619.

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the prevalence of polydipsia in autism compared with mental deficiency, as well as the influence of psychotropic drugs and residential factors on the water drinking behavior.

2. Patients and methods The subjects were 138 children (96 boys and 42 girls), who were attending schools for handicapped children in Fukui prefecture. All the patients were diagnosed as having autism or mental retardation by medical doctors at the Center of Developmental Medicine and Education for Handicapped Children in Fukui Prefecture. Forty nine children with autism (autistic group: 6.6–18.8 years; mean, 13.8 years; standard deviation (SD), 3.4 years; 41 boys and eight girls) met the criteria for autistic disorder of the Diagnostic and Statistical Manual of Mental Disorders, 3rd edition, revised (DSM-III-R) [7]. In DSM-III-R, there is no intelligence quotient (IQ) level that rules out an autistic disorder. In the ordinary way, according to DSM-

 1999 Elsevier Science B.V. All rights reserved.

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Table 1 Severity scores for water drinking behavior Scores

1. 2. 3. 4.

Frequency of drinking water Duration of standing in front of water supply Intake of water Frequency of requesting water

2

1

0

Many times an hour More than 30 min a day More than 5 l a day Many times an hour

Many times a day Less than 30 min a day Less than 5 l a day Many times a day

A few times a day Less than 5 min a day Less than 2 l a day A few times a day

III-R, profoundly mentally retarded patients with an autistic tendency are diagnosed as having an autistic disorder. However, since almost all the patients in this study were followed by a child psychiatrist (second author) and the developmental history in infancy had been taken down by him in detail, we seldom confused profound mental retardation with autism. The control subjects were 89 children with mental retardation (retarded group: 6.9–18.6 years; mean, 12.8 years; SD, 3.9 years; 55 boys and 34 girls) who met the DSM-III-R criteria for mental retardation. However, this retarded group was restricted to physiological mental retardation. After written consent for the present study had been obtained from each of the committees of the four schools, attended by the patients, we sent a questionnaire to each school in February 1994. The subjects were only identified according to the birth date, in order to protect their privacy. The questionnaire consisted of items regarding birth date, medication, IQ as estimated the Tanaka-Binet test, residential situation, severity score for water drinking behavior given by us (Table 1), and the severity of the polydipsia based on Matsuda’s criteria [8]. The residential situations were divided into ‘at home’ and ‘not at home’ to indicate whether the children were living in institutions for the mentally handicapped or living in residential facilities attached to the schools. The questionnaires were collected, and the severity scores for water drinking behavior were calculated, the sum of which was made to range from 0 to 8 points (Table 1). The severity of the polydipsia was judged according to Matsuda’s criteria, i.e. ‘severe’, ‘moderate’ and ‘mild’. If a patient has one or more of the following four symptoms, he or she is judged as having ‘severe polydipsia’. (1) Children gulp down water without turning off the water supply (2) they drink all the water in a kettle within 30 min (3) their clothes are constantly wet and (4) in spite of being told not to drink, they continue to drink. Children who carry a glass and stand at a water supply are judged to be ‘moderately’ polydipsic. Children who drink a large amount of water at certain times a day are judged as being ‘mildly’ polydipsic. Differences in the prevalence of polydipsia between autistic and control children were assessed with the x2 test. Mann–Whitney’s U test was used to assess the significance of differences in the severity differences in severity

scores between the groups. Differences in the prevalence of polydipsia between ‘at home’ and ‘not at home’ were assessed with Fisher’s exact probability test for four-fold tables. Statistical significance was defined as P , 0.05. In addition, the IQ had been given in the collected questionnaires for ten of the 49 subjects with autism and 25 of the 89 mentally retarded children. The mean IQs were 51 (range, 23 to 71; SD, 14) and 36 (range, 15 to 64; SD, 12) in the autistic and mentally retarded groups, respectively.

3. Results The number of patients with and without polydipsia based on Matsuda’s criteria in the two groups are shown in Table 2. Eight of the 49 autistic children (16.3%) were considered to have polydipsia, compared with six of the 89 (6.7%) mentally retarded children. This difference was not statistically significant (x2 = 3.19, P = 0.074), even though polydipsia was twice as prevalent in the autistic group. Only two of the eight autistic patients with polydipsia had been taking psychotropic drugs (Table 2). The remaining six patients, including three with severe or moderate polydipsia, had polydipsia without receiving psychotropic drugs. In the mentally retarded group, two of six patients with polydipsia had been taking the psychotropic drug (Table 2). The remaining four patients, including one with severe polydipsia, had been taking no psychotropic drugs. Each of the four medicated patients was taking a single psychotropic drug: carbamazepine, clonazepam, pentoxifylline, and an unknown drug, respectively. The number of patients with each severity score, 0–8 points, for water drinking behavior are shown in Table 3. The average scores were 0.67 (SD, 1.18) and 0.33 (SD, Table 2 Prevalence of polydipsia Autistic group (N = 49)

Retarded group (N = 89)

Polydipsia On psychotropic drugs

8 (16.3%) 2

6 (6.7%) 2

No polydipsia On psychotropic drugs

41 (83.7%) 3

83 (93.3%) 24

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K. Terai et al. / Brain & Development 21 (1999) 103–106 Table 3 Number of subjects with each severity score for water drinking behavior Number of subjects with each score (%)

Autistic group Retarded group Total

Total

0

1

2

3

4

5–8

33 75 108

7 (14.3) 7 (7.9) 14

4 (8.2) 2 (2.2) 6

2 (4.1) 2 (2.2) 4

3 (6.1) 3 (3.4) 6

0 0 0

0.90) in the autistic and mentally retarded groups, respectively, the score being significantly higher in the former (P = 0.022). The number of patients with and without polydipsia in the two groups based on Matsuda’s criteria in the two different residential situations, i.e. ‘at home’ and ‘not at home’, are shown in Table 4. In the autistic group, six of the 29 patients (20.7%) who were ‘not at home’ had polydipsia, whereas only two of the 20 patients (10%) ‘at home’ had polydipsia. However, the difference in the incidence of polydipsia was not statistically significant (P = 0.47). In the retarded group, four of the 51 patients (7.8%) ‘not at home’ showed polydipsia in contrast to only two of the 34 patients (5.9%) ‘at home’. Therefore, there was no significant difference between these incidences (P = 0.54). No significant difference was found in either group.

4. Discussion The present study indicates that polydipsia tends to occur somewhat more often in autism than in mental retardation, and is significantly more severe in autism. Bremner et al. [9] studied 877 mentally handicapped inpatients. In their study, the prevalence of polydipsia in autism was 27.2% (six of 22 cases), compared with 16.3% in the present study. Furthermore, they described a case of autism with fatal water intoxication, who was taking fluvoxamine and chlorpromazine, but did not discuss the role of the drugs as a cause of polydipsia. Autism has been stated to be associated with a hypothalamic-pituitary dysfunction indicated by a blunted-plasma growth-hormone response following the oral administration

49 89 138

of l-dopa[10], an abnormal plasma growth hormone response to insulin-induced hypoglycemia [11], and a premature or delayed response of growth hormone to clonidine and l-dopa [12]. The blunted growth hormone response exhibited by at least 30% of autistic children to a provocative challenge with l-dopa suggests an alternation of hypothalamic dopamine receptor sensitivity (subsensitivity) in autistic children [10]. The premature response of growth hormone to clonidine and delayed response to l-dopa suggest possible abnormalities of both dopaminergic and noradrenergic neurotransmission in subjects with autism [12]. Furthermore, Hiratani et al. described a case of autism with water intoxication and the episodic release of antidiuretic hormone [13]. The thirst center is said to be located in the hypothalamus. Therefore, a possible factor causing polydipsia in autism may be a hypothalamic–pituitary dysfunction. In 1988, the male case described by Hiratani et al. [13], who was 19-years old at that time, exhibited a remarkable daily body weight change that was probably due to excessive water drinking. After mild water restriction and intermittent forced water restriction according to the setting of a body weight limit, the daily change became smaller in 1994 [14]. We have often observed that autistic children sometimes fiddle with water, or only drink from a single faucet, presumably one manifestation of the restricted interest characteristic of autism. Therefore, preservative tendencies may contribute to compulsive water drinking. In conclusion, in view of the present results, it is possible that the principal cause of polydipsia is some intrinsic factor in autism itself (e.g. a hypothalamic–pituitary dysfunction, restricted interest and activity).

Table 4 Numbers of subjects with and without polydipsia in different residential situations Number of drinkers (%)

Number of non-drinkers (%)

Total (%)

Autistic group At home Not at home

2 (4.1) 6 (12.2)

18 (36.7) 23 (46.9)

20 (40.8) 29 (59.2)

Retarded group At home Not at home Unknown residential situation

2 (2.2) 4 (4.5) 0

32 (36.0) 47 (52.8) 4 (4.5)

34 (38.2) 51 (57.3) 4 (4.5)

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Finally, it is important for medical and teaching staff to be aware of the signs of polydipsia in autistic children.

Acknowledgements The authors wish to thank the staff at the schools for handicapped children. A summary of this study was presented at the 35th Chubu part of the Japanese Society of Psychosomatic Medicine (Nagoya, Japan), May 13, 1995.

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