A general population-based study involving tricyclic antidepressants and selective serotonin reuptake inhibitors suggests that the observed increase in risk for a first myocardial infarction is related to the underlying depression rather than a drug effect, according to an article in the April issue of the journal Heart. More than 10 percent of older people are taking an antidepressant medication.

The findings are based on anonymous prescribing supplied from 644 general practices across the UK, on 60,000 patients who had had their first myocardial infarction between 1998 and 2001 and 360,000 randomly selected other adults, matched for age and sex.

Analysis indicated an increased risk of a first myocardial infarction with either the newer or older class of antidepressants within the first month of prescription.
Patients who had been prescribed tricyclic antidepressants for the first time were twice as likely to have a myocardial infarction within the next seven days as patients who had not been prescribed these drugs.

Patients prescribed selective serotonin reuptake inhibitors were over twice as likely to have an infarction within the next seven days.

However, the increased risks for myocardial infarction were much lower among patients who took antidepressants for longer than a month. These risks disappeared after taking account of the extent of existing cardiovascular disease and depression, which was gleaned from looking at prescription data before and after the myocardial infarction (known as self controlled analysis).

The authors also failed to find any link with specific antidepressants or with the class of drug, leading them to conclude that any increase in risk is more likely to be linked to the underlying depression rather than the drugs themselves.