Familial aggregation of depression, but no familial aggregation of individual depressive symptoms.
BACKGROUND
Familial aggregation of major depression might indicate a genetic liability for the disorder. The complete disorder or, alternatively, only some individual symptoms might be inherited. Under the latter condition, an increased frequency of inherited symptoms might consecutively increase the likelihood to reach the threshold for depression in relatives and, thus, might cause the familial aggregation of depression. Up to now, no study investigated the possibility of a relationship between individual depressive symptoms and the familial aggregation of depression.


METHODS
The familial aggregation of early-onset depression (age-at-onset < 60 years, EOD) but less so of late-onset depression (LOD) has been shown in this sample. To assess the hypothesis of an inheritance of individual depressive symptoms as a possible cause of the familial aggregation of depression, frequencies of symptoms were compared in relatives of depressed patients and of controls using forward logistic regression analyses.


RESULTS
Some individual depressive symptoms showed clustering in relatives of patients with depression, but the pattern of inheritance was inconsistent, i.e. the clustering of symptoms was different between non-depressed and depressed relatives of patients with EOD and LOD, respectively. No intra-familial clustering of specific depressive symptoms within families of depressed subjects could be observed.


CONCLUSIONS
Due to the inconsistencies in the clustering of individual symptoms in non-depressed and depressed relatives and the lack of intra-familial clustering, the familial aggregation of depression is unlikely to be caused by the aggregation of individual depressive symptoms. An inheritance of the vulnerability for complete depressive disorders influenced by environmental factors is more likely.
Heun
Reinhard
R
The University of Birmingham, Division of Neuroscience, Queen Elizabeth Psychiatric Hospital, Mindelsohn Way, Birmingham B15 2QZ, United Kingdom. r.heun@bham.ac.uk
Hein
Sandra
S
D000367:Age Factors; D017668:Age of Onset; D000368:Aged; D000704:Analysis of Variance; D003866:Depressive Disorder / Q000175:diagnosis / Q000235:genetics* / Q000523:psychology*; D005190:Family / Q000523:psychology*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000523:psychology; D005858:Germany; D006801:Humans; D007406:Interview, Psychological; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012016:Reference Values; D012306:Risk