PEDIATRICS Vol. 121 No. 5 May 2008, pp. e1357-e1362 (doi:10.1542/peds.2007-2296)
ARTICLE |
Parental Psychiatric Disorders Associated With Autism Spectrum Disorders in the Offspring
a Departments of Epidemiology and Maternal and Child Health, University of North Carolina, Chapel Hill, North Carolina
b Department of Medical Epidemiology and Biostatistics
d Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
c Department of Community and Preventive Medicine and Institute for Epidemiology, Biostatistics, and Prevention, Mount Sinai School of Medicine, New York, New York
 |
ABSTRACT |
|---|
 TOP ABSTRACT METHODSRESULTSDISCUSSIONREFERENCES |
|---|
OBJECTIVE. Autism is a developmental disorder defined by impaired social interaction, communication, and behavior. Causes and correlates of autism are largely unknown, but elevated frequencies of psychiatric disorders and distinct personality traits have been reported among the family members of individuals with autism. Linkage of data from Swedish registries was used to investigate whether hospitalization for psychiatric conditions was higher among parents of children with autism compared with control subjects.
METHODS. Data sources included the Swedish Medical Birth Register (child's birth), the Swedish Multi-Generation Register (linking parents to children), and Swedish Hospital Discharge Register (hospitalization records). Children born between 1977 and 2003 who had a hospitalization record indicating autism before 10 years of age (n = 1227) were matched with 30 693 control subjects from the Swedish Medical Birth Register by gender, year of birth, and hospital. Parent diagnoses were based on an inpatient hospital diagnostic evaluation and included schizophrenia, other nonaffective psychoses, affective disorders, neurotic and personality disorders and other nonpsychotic disorders, alcohol and drug addiction and abuse, and autism. Odds ratios and 95% confidence intervals were estimated by using conditional logistic regression, adjusted for child's age, gender, hospital of birth, parents’ age, country of birth and socioeconomic status, and diagnosis of a mental disorder in the other parent.
RESULTS. Parents of children with autism were more likely to have been hospitalized for a mental disorder than parents of control subjects. Schizophrenia was more common among case mothers and fathers compared with respective control parents. Depression and personality disorders were more common among case mothers but not fathers.
CONCLUSIONS. This large population study supports the potential for familial aggregation of psychiatric conditions that may provide leads for future investigations of heritable forms of autism.
Key Words: autism • psychiatric disorders • schizophrenia • depression • epidemiology • registry
Abbreviations: ICD—International Classification of Diseases • OR—odds ratio • CI—confidence interval
Autism is a developmental disorder defined by impaired social interaction, communication, and behavior.1 The strong genetic contribution to autism has been well supported by twin studies noting high concordance among monozygotic twins.2 However, the etiology of autism is complex and likely involves multiple genes in combination with external factors.3–6 This allows for the possibility that autism and other psychiatric disorders result from some common genes, possibly varying in expression and in combination with other factors.
Personality traits similar to, but not as severe as, the defining features of autism have been found to be more common among the family members of some individuals with autism. These subclinical traits have become known as the broader autism phenotype.7–12 In addition, elevated rates of clinical psychiatric disorders, distinct from autism, have been reported among the relatives of individuals with autism, including schizophrenia, anxiety, depression, and social phobias.13–18 Specific genes that might contribute to the complex constellation of factors leading to autism or other psychiatric disorders have yet to be confirmed.4,19 However, identifying specific psychiatric disorders among the parents of individuals with autism could help distinguish familial cases from sporadic cases. This study evaluates whether hospital diagnosis of psychiatric disorders is more common among the parents of children with hospital-diagnosed autism than the general population, and, if so, which disorders are most strongly associated with autism.
|
METHODS |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
A population-based case-control study was nested within a Swedish cohort of children born between 1977 and 2003 and their parents. Several Swedish registries were linked to facilitate the study. All of the linkages were possible because of the unique national registration number that is assigned to all Swedish residents at the time of birth or immigration and is consistently used in all types of registers and registrations in Sweden.20 First, children with a diagnosis of autism were identified through the Swedish Hospital Discharge Registry. This register has nearly complete nationwide coverage for inpatient hospital care for psychiatric disorders from 1973 onward and records the treating physician's discharge diagnosis on the basis of the International Classification of Diseases (ICD).20 The Swedish health care system has a strong network among outpatient service, inpatient care, and school health service for individuals with autism and psychiatric conditions. No private clinics are used.
Children were considered case subjects if they were born between 1977 and 2003 and had a diagnosis of autism disorder, Asperger syndrome, or pervasive developmental disorder not-otherwise-specified at or before 10 years of age that was recorded in the registry between 1987 and 2003 (see Appendix for ICD classification).
|
Case children were linked by the unique registration number to the Swedish Medical Birth Registry, operated by the National Board of Health and Welfare. From the same registry, 25 control children were randomly selected for each case subject from among children of the same gender, birth year, and birth hospital. The control subjects were alive and did not have any hospital diagnosis consistent with autism at the time of the diagnosis of their respective case.
All of the children were linked to their biological parents through the Swedish Multi-Generation Register, which contains familial relationship data and is maintained by Statistics Sweden. The register contains entries for an "index person," along with the biological parents. To be included in the register, an index person had to be registered in Sweden after 1961 and to have been born after 1932. Paternity is assumed to be the husband of the mother at the time of birth or "by acknowledgment" for unwed mothers. Parents were then linked back to the Swedish Hospital Discharge Register to identify inpatient hospital diagnoses related to the parent's psychiatric disorders. Parents’ diagnoses were classified into categories defined a priori to cover psychotic and nonpsychotic psychiatric disorders including schizophrenia, affective disorders, other nonaffective psychoses, neurotic and personality disorders and other nonpsychotic disorders, alcohol and drug addition/abuse, and autism (see Appendix for ICD classification). Records between 1968 and 2003 were extracted for each parent from the Swedish Hospital Discharge Register, and additional data on the parents’ socioeconomic status and country of birth was obtained from Statistics Sweden.
The timing of both children's and parent's diagnoses was defined as the year of first recorded diagnosis. For parents who had multiple diagnoses, the year could have varied in the analysis depending on whether the model was specifying "any" disorder or a specific disorder subgroup. To evaluate the timing of the parent's diagnosis relative the child's diagnosis, the year of the case child's first diagnosis served as the reference year for both the case and the matched control subjects.
Conditional logistic regression analyses estimated odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for child's age, gender and hospital of birth, parents’ age at delivery, socioeconomic status, country of birth, and any mental disorder for the other parent. The study was approved by the University of North Carolina at Chapel Hill Office of Human Research Ethics Institutional Review Board and by the Karolinska Institutet Research Ethics Committee.
|
RESULTS |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Both biological parents were linked for 1227 (99%) of 1237 identified case subjects and 30 693 (99%) of 30 925 identified control subjects. Seventy-seven percent of the children were boys. Half were 4 to 6 years of age at the time of diagnosis or reference date, 20% were <4 years of age, and 30% were >6 years of age. Parents of case and control subjects were of similar socioeconomic status, but case subject parents were generally more likely to be of African, Asian, and South American nativity compared with Nordic nativity. The fathers of children with autism were older than control fathers (Table 1).
|
Overall, psychiatric disorders were more common among the parents of children with autism than among the parents of control subjects (OR: 1.7; 95% CI: 1.5–2.0). The OR for autism was slightly greater if both parents had been diagnosed with a psychiatric disorder (OR: 2.0; 95% CI: 1.2–3.1), adjusted for child's age, gender, reference year, parental age, socioeconomic status, and country of birth (data not shown in tables).
Schizophrenia among both the mothers (OR: 1.9; 95% CI: 0.8–4.7) and the fathers (OR: 2.1; 95% CI: 0.9–4.9) was associated with autism in their children (Table 2). Among mothers, depression (OR: 1.7; 95% CI: 1.0–2.6) and neurotic and personality disorder and other nonpsychotic disorders (OR: 1.7; 95% CI: 1.3–2.2) were associated with increased risk of autism among the children but not among the fathers. Other evaluated parental psychiatric disorders were not associated with autism in the children. Associations between parental psychiatric disorders and autism did not vary by the child's birth order or by the early (1987–1996) versus the late (1997–2004) cohorts, in which the diagnostic practices might have differed (data not shown).
|
The positive association between any parental psychiatric disorder and the child's diagnosis of autism was present regardless of the timing of the parent's diagnosis relative to the child's diagnosis (Table 3). The ORs for autism were slightly higher if the parent had been diagnosed before the child's diagnosis or before the child's birth, rather than after.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
In these data, parental psychiatric diagnoses in the aggregate were associated with a twofold increased risk of autism among the children. For both parents, schizophrenia was associated with autism. For other disorders, such as depression and nonpsychotic personality disorders, the positive association between psychiatric disorders and childhood autism was found only for maternal disorders, not for paternal disorders.
We hypothesized that having a psychiatric condition might influence parents to have their child evaluated for psychiatric conditions and consequently result in increased diagnosis of autism or, conversely, that a child's disorder may lead to depression among the parents and elevate the association between the parent's and child's diagnosis. The magnitude of the association between any parental diagnosis and autism was higher when the parent's diagnosis was set before the child's but remained elevated for maternal psychiatric diagnoses after the child's birth and diagnosis. This temporal analysis may indicate some modest increase in the children's rate of diagnosis if the parents were already in the psychiatric care system and counters that parental difficulty resulting from caring for the child's disorder would increase depression or other clinical psychiatric symptoms. These results support the hypothesis that there is a familial predisposition, perhaps genetic, that presents differently in the parent than in the child and probably requires a constellation of other genetic or environmental factors for expression.
These results are consistent with other studies that have shown associations between parent's psychiatric disorders and children's diagnosis of autism; however, the specific disorders associated with autism vary by study and may reflect methodologic differences.21 The study most similar to this study, which also relied on population-based record linkage, reported a nearly threefold increased risk of autism associated with parental schizophrenia, affective disorder, and an "other" category of disorders but was unable to distinguish whether maternal or paternal diagnoses were responsible for the association.13 These results may be consistent with our finding of an association with schizophrenia in both parents and depression among mothers, but detail is lacking for full comparison. Other case-control studies have implicated various psychiatric disorders, including schizophrenia, depression, social phobia, and affective disorder, but results have been inconsistent, and the smaller sample sizes have limited the ability to consistently distinguish the diagnostic categories most associated with autism.14–17 The social impairments and adherence to rigid routines experienced by individuals with autism may reflect a more severe presentation of social discomfort and the interpersonal challenges common to those with anxiety disorders and schizophrenia. Studies of altered brain morphology and candidate genes have been inconsistent but suggestive for both disorders.4,22–25 Distinguishing familial cases of autism, characterized by a family history of psychiatric disorders, may enhance progress in understanding whether some anatomic and genetic factors are common to both disorders.
The variability in results among the studies has been attributed to differences in the diagnostic standards for the children, reporting bias in classifying the parents, and the characteristics of the study population and control selection.21 The present study relied on diagnoses recorded in the Swedish Hospital Discharge Register. The register represents nationwide coverage of inpatient treatment facilities during the study period and includes care in psychiatric hospitals, child psychiatric clinics, special units for treatment of autism disorders, and pediatric and other somatic clinics but does not include case subjects only diagnosed and treated as outpatients. During the majority of the period under evaluation, it was common for children suspected of autism in Sweden to be hospitalized for more careful diagnostic evaluation, but in the 1990s, outpatient evaluation and treatment began to replace services that were previously conducted in the hospitals. The temporal analysis indicates that it is unlikely that an association with hospitalized autism would be artificially induced because of a shift from outpatient to inpatient treatment over time. An earlier study of autism using the Swedish Hospital Discharge Register estimated inclusion of 
50% of expected case subjects on the basis of prevalence figures of Gillberg and Wing26 and Fombonne,27 considering the study period, geographic area, definition of autism, and age of case subjects.20 Because all residents have equal access to both inpatient and outpatient services that are well coordinated, the decision about whether the child is hospitalized is unlikely to be related to parental resources or abilities (including psychiatric diagnoses). The present study was unable to validate the diagnoses in the registry by personal review, but the discharge diagnosis, which is the basis for the register data, reflects the final assessment by a psychiatric specialist. A previous validation of schizophrenia diagnoses indicated that registry data were reliable and valid for psychiatric research,28 but such a validation has not been conducted for autism.
Diagnostic practices in psychiatry continue to change, and case definitions become more narrow for both adult and childhood psychiatric disorders. Thus, it will be important to assess the relationships between parental psychiatric disorders and an offspring's risk of autism in other data with more detailed and complete ascertainment of psychiatric disorders for parents and offspring.
Analyses based on hospital diagnoses recorded in the registry may miss more mildly affected individuals, among both parents and children, consequently reflecting more severe cases of autism and parental psychiatric disorders. Accordingly, the generalizability of the results might be somewhat limited to associations among psychiatric diagnoses severe enough to require hospitalization. We could not evaluate parents with mild disorders treated as outpatients or those with subclinical personality traits consistent with the broader autism phenotype. The influence of misclassified autism case subjects was diminished, however, because control subjects were oversampled from the population. Given the nature of these design limitations, the reported associations between parental and child psychiatric conditions are likely to be underestimates of the extent of these relationships within families.
Despite these limitations, the study benefits from its large size and population representation. Most other reports reflect a select group of clinical participants and often compare autism case subjects with control subjects with other disabilities.14–17 This population-based study was possible because of universal access to health care and availability of disease and demographic characteristics for the entire base population. The registries cover >99% of the Swedish population with essentially complete linkage among parents, children, and hospital discharge data.20 Although the details of the parent's and child's diagnoses are limited in such data sets, they are not likely to be biased by recall and reporting differences among case and control subjects. Data in these registers allowed control for parental characteristics shown to be associated with autism by other studies, such as immigrant status and paternal age. In addition, the size and population representation improve precision in estimating the relationship among these rare diagnoses in a less select population than in some previously published research.
These results support those of smaller studies that indicated an increase in psychiatric conditions among parents of children with autism, specifically schizophrenia, neurotic disorders, and depression. Identifying families with a propensity for rare psychiatric conditions may help uncover rare genes that contribute to the susceptibility of both disorders. Future studies that have the ability to contact families directly for detailed information should confirm both parent's and child's diagnosis, consider more extended family members, and consider more mild psychiatric conditions treated on an outpatient basis, as well as subclinical personality traits consistent with the broader autism phenotype, which were not assessed here. It will also be important to reevaluate these findings among children with more mild symptoms of autism.
|
ACKNOWLEDGMENTS |
|---|
This work was supported partially by the Centers for Disease Control and Prevention.
|
FOOTNOTES |
|---|
Accepted Nov 12, 2007.
Address correspondence to Julie L. Daniels, MPH, PhD, Department of Epidemiology, CB 7435, University of North Carolina, Chapel Hill, NC 27599-7435. E-mail: juliedaniels{at}unc.edu
The authors have indicated they have no financial relationships relevant to this article to disclose.
| What's Known on This Subject Previous literature has noted that psychiatric disorders are more common among family members of individuals with autism. Previous studies have used small clinic-based samples and been unable to distinguish whether associations are more common among mothers or fathers.
|
| What This Study Adds The Swedish registry system allowed data linkage to study a population less prone to selection bias than previous clinical samples. This large, population-based study had power to distinguish associations between psychiatric history among mothers versus fathers in relation to autism.
|
|
REFERENCES |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
1. American Psychiatric Association, Task Force on DSM-IV. Diagnostic and Statistical Manual of Mental Disorders: DSM-IV-TR. 4th ed. Washington, DC: American Psychiatric Association; 2000
2. Folstein S, Rutter M. Infantile autism: a genetic study of 21 twin pairs. J Child Psychol Psychiatry. 1977;18 (4):297 –321[Web of Science][Medline]
3. Muhle R, Trentacoste SV, Rapin I. The genetics of autism. Pediatrics. 2004;113 (5). Available at: www.pediatrics.org/cgi/content/full/113/5/e472
4. Newschaffer CJ, Croen LA, Daniels J, et al. The epidemiology of autism spectrum disorders. Annu Rev Public Health. 2007;28 :235 –258[CrossRef][Web of Science][Medline]
5. Lauritsen M, Ewald H. The genetics of autism. Acta Psychiatr Scand. 2001;103 (6):411 –427[CrossRef][Web of Science][Medline]
6. Folstein SE, Rutter ML. Autism: familial aggregation and genetic implications. J Autism Dev Disord. 1988;18 (1):3 –30[CrossRef][Web of Science][Medline]
7. Bolton P, Macdonald H, Pickles A, et al. A case-control family history study of autism. J Child Psychol Psychiatry. 1994;35 (5):877 –900[Web of Science][Medline]
8. Piven J, Palmer P, Jacobi D, Childress D, Arndt S. Broader autism phenotype: evidence from a family history study of multiple-incidence autism families. Am J Psychiatry. 1997;154 (2):185 –190[Abstract]
9. Hurley RS, Losh M, Parlier M, Reznick JS, Piven J. The broad autism phenotype questionnaire. J Autism Dev Disord. 2007;37 (9):1679 –1690[CrossRef][Web of Science][Medline]
10. Murphy M, Bolton PF, Pickles A, Fombonne E, Piven J, Rutter M. Personality traits of the relatives of autistic probands. Psychol Med. 2000;30 (6):1411 –1424[CrossRef][Web of Science][Medline]
11. Constantino JN, Todd RD. Autistic traits in the general population: a twin study.
Arch Gen Psychiatry. 2003;60
(5):524
–530
12. Constantino JN, Todd RD. Intergenerational transmission of subthreshold autistic traits in the general population. Biol Psychiatry. 2005;57 (6):655 –660[CrossRef][Web of Science][Medline]
13. Larsson HJ, Eaton WW, Madsen KM, et al. Risk factors for autism: perinatal factors, parental psychiatric history, and socioeconomic status.
Am J Epidemiol. 2005;161
(10):916
–925; discussion 926–918
14. Bolton PF, Pickles A, Murphy M, Rutter M. Autism, affective and other psychiatric disorders: patterns of familial aggregation. Psychol Med. 1998;28 (2):385 –395[CrossRef][Web of Science][Medline]
15. Bolte S. A case-control study of personality style and psychopathology in parents of subjects with autism. J Autism Dev Disord. 2007;37 (2):243 –250[CrossRef][Web of Science][Medline]
16. Piven J, Palmer P. Psychiatric disorder and the broad autism phenotype: evidence from a family study of multiple-incidence autism families.
Am J Psychiatry. 1999;156
(4):557
–563
17. Piven J, Gayle J, Chase GA, et al. A family history study of neuropsychiatric disorders in the adult siblings of autistic individuals. J Am Acad Child Adolesc Psychiatry. 1990;29 (2):177 –183[Web of Science][Medline]
18. Piven J, Chase GA, Landa L, et al. Psychiatric disorders in the parents of autistic individuals. J Am Acad Child Adolesc Psychiatry. 1991;30 (3):471 –478[Web of Science][Medline]
19. Newschaffer CJ, Fallin D, Lee NL. Heritable and nonheritable risk factors for autism spectrum disorders.
Epidemiol Rev. 2002;24
(2):137
–153
20. Hultman CM, Sparen P, Cnattingius S. Perinatal risk factors for infantile autism. Epidemiology. 2002;13 (4):417 –423[CrossRef][Web of Science][Medline]
21. Yirmiya N, Shaked M. Psychiatric disorders in parents of children with autism: a meta-analysis. J Child Psychol Psychiatry. 2005;46 (1):69 –83[CrossRef][Web of Science][Medline]
22. Rojas DC, Peterson E, Winterrowd E, Reite ML, Rogers SJ, Tregellas JR. Regional gray matter volumetric changes in autism associated with social and repetitive behavior symptoms. BMC Psychiatry. 2006;6 :56[CrossRef][Medline]
23. Fatemi SH, Reutiman TJ, Folsom TD, Sidwell RW. The role of cerebellar genes in pathology of autism and schizophrenia. Cerebellum. 2007:1 –16
24. Stanfield AC, McIntosh AM, Spencer MD, Philip R, Gaur S, Lawrie SM. Towards a neuroanatomy of autism: a systematic review and meta-analysis of structural magnetic resonance imaging studies. Eur Psychiatry. 2007; PMID: 17765485
25. Wassink TH, Hazlett HC, Epping EA, et al. Cerebral cortical gray matter overgrowth and functional variation of the serotonin transporter gene in autism.
Arch Gen Psychiatry. 2007;64
(6):709
–717
26. Gillberg C, Wing L. Autism: not an extremely rare disorder. Acta Psychiatr Scand. 1999;99 (6):399 –406[Web of Science][Medline]
27. Fombonne E. The epidemiology of autism: a review. Psychol Med. 1999;29 (4):769 –786[CrossRef][Web of Science][Medline]
28. Dalman C, Broms J, Cullberg J, Allebeck P. Young cases of schizophrenia identified in a national inpatient register–are the diagnoses valid? Soc Psychiatry Psychiatr Epidemiol. 2002;37 (11):527 –531[CrossRef][Web of Science][Medline]
PEDIATRICS (ISSN 1098-4275). ©2008 by the American Academy of Pediatrics
CiteULike 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  R. A Kumar, J. Sudi, T. D Babatz, C. W Brune, D. Oswald, M. Yen, N. J Nowak, E. H Cook, S. L Christian, and W. B Dobyns A de novo 1p34.2 microdeletion identifies the synaptic vesicle gene RIMS3 as a novel candidate for autism J. Med. Genet., February 1, 2010; 47(2): 81 - 90. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. K. Grether, M. C. Anderson, L. A. Croen, D. Smith, and G. C. Windham Risk of Autism and Increasing Maternal and Paternal Age in a Large North American Population Am. J. Epidemiol., November 1, 2009; 170(9): 1118 - 1126. [Abstract] [Full Text] [PDF]
|
|
eLetters:
Read all eLetters
- Request Clarification on Hospitalization Occurrence
- Shelly D. Sulkoske
- Pediatrics Online, 5 May 2008 [Full text]
- Denial of Proper Health Care for Children Labeled as Autistic
- Michael F. Wagnitz, et al.
- Pediatrics Online, 8 May 2008 [Full text]
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
