Family history of psychiatric disorder generally predicts the simple presence vs absence of that disorder among probands.1–8
However, there is a need to go further and test whether family history is also associated with clinical features of the disorder thought to represent a continuum of seriousness among individuals who meet criteria for diagnosis.
This article reports a test of the hypothesis that family history is associated with clinical indicators of a disorder’s developmental course (younger age at onset, more frequent recurrence) and health burden (worse impairment, more service use). Evidence that family history is associated with such seriousness indicators could inform both clinical practice and research design. First, if family history is associated with clinical features that are thought to index seriousness of disorder, then family history could be used prognostically to determine which patients will have the poorest outcome, and scarce treatment resources could be directed to patients with a positive family history of their disorder. Second, if family history is associated with certain clinical features, then those features might be inferred to indicate a form of disorder that is under greater genetic influence, and researchers might benefit from selecting individuals with those features for genetic studies.8
There are 3 notable research gaps. First, although a number of clinical features have been investigated in relation to family history of depression,3,9–13
other psychiatric disorders have been less well studied. There is a need for systematic investigation of the association between clinical indexes and family history across a broader range of disorder types. For example, for anxiety disorder, alcohol dependence, and drug dependence, there have been, to our knowledge, no family history studies reporting on recurrence of disorder and only a handful of studies reporting on impairment or use of mental health services.14–17
Second, there is a need to compare the association between clinical features and family history across multiple different disorders, but within the same cohort of families. Although a handful of studies have assessed familial aggregation across different disorders within the same sample,1,18
to our knowledge no study has sought to compare associations with clinical features across different disorders. Methodologic differences in sampling, design, measurement, and statistical approach among single-disorder studies have made it difficult to discern whether different disorders show the same or distinctive patterns of family history effects. A systematic investigation using one cohort of families would allow us to compare the direction of effects and effect sizes for family history’s effects on different disorders, while holding constant aspects of the study methods.
Third, there is a need to assess clinical features beyond age at onset. Age at onset is probably the only clinical feature that has been well studied in relation to family history across different disorders. Most studies have reported significant associations between early onset of disorder and family history of depression,10,13,19–42
and drug dependence.60,61
However, some researchers have failed to find an association (eg, for depression,9,11,62–70
and drug dependence17
). Moreover, far less is known about associations between family history and other clinical features such as recurrence, impairment, and service use that may also indicate seriousness of disorder. We are aware that these 4 indicators are influenced by factors apart from seriousness; for example, measures of service use are influenced, in part, by access to health care. Nevertheless, we focus on these 4 clinical features because earlier onset of disorder leads to impaired social functioning,74
frequent recurrence of disorder disrupts long-term adult adjustment,75
self-reported impairment indicates that the disorder has subjectively interfered with personal goals, and service use indicates greater burden on health care systems.
In the present study, we tested hypotheses that family history would be associated with 4 clinical indexes of a disorder (recurrence, impairment, service use, and age at onset) in relation to 4 psychiatric disorders (major depressive episode, anxiety disorder, alcohol dependence, and drug dependence) in a birth cohort of 32-year-olds.