The aetiology of depression in first myocardial infarction patients.

Background:Depression affects outcome following myocardial infarcation but the risk factors for such depression has been little studied. This study considered whether the causes of depression occuring before and after myocardial infarction were similar to those of depression in the general population.Method:Consecutive patients admitted to hospital following their first myocardial infarction were interviewed with the Schedule for Clinical Assessment in Neuropsychiatry (SCAN) to detect psychiatric disorders and the Life Events and Difficulties Schedule (LEDS) to assess recent stress. Participants completed the Hospital Anxiety and Depression Scale at entry to the study and one year later and the risk factors associated with a high score at both times were assessed.Results:314 (88% of eligible) patients were recruited; 63% were male. 63 (20%) had depressive disorders. Logistic regression identified the following as independently associated with depressive disorder that had been present for at least one month before the myocardial infarction: younger age (OR-0.95), female sex (OR=2.3), past psychiatric history (OR=5.7), social isolation (OR=4.7), having marked non-health difficulties (OR=2.4) and lack of a close confidant (OR=9.2). At follow-up 269/298 (90%) responded; of 189 participants not depressed at first assessment, 39 (21%) became depressed by the one year follow-up. Logistic regression identified frequent angina (OR=0.96) as the only significant predictor of raised HAD scores at 12 months.Conclusions:Depression developing during the year following myocardial infarction does not have the same risk factors as that which precedes myocardial infarction. Further clarification of the mechanisms linking depression to poor outcome may require separation consideration of pre- and post-myocardial infarction depression, and its risk factors.