Research has shown people who have a heart attack are more likely to become depressed which puts them at risk for another heart attack.
But a study of more than 1,100 patients found quitting smoking more than doubled the chance of improving post-heart attack depression.
Patients who were physically active before their heart attack were also more likely to improve their depression.
Depressive symptoms in cardiac patients may differ from psychiatric patients.
Rather than feeling sad or hopeless, they complain of insomnia, fatigue or body pain.