Recovering from a heart attack can be tough, but new research suggests that depression, anxiety and stress can make it even tougher.

"Anxiety may lead to fear of another cardiac event and stop people from being active," said study author Angela Rao, from the University of Technology Sydney in Australia. "Depression and anxiety can also impair the ability to retain new information needed to make health-related behavior changes."

Rao's team followed nearly 4,800 patients undergoing cardiac rehabilitation at two Sydney hospitals between 2006 and 2017.

A mental health assessment showed that 18% 28% and 13% of the patients had moderate to extremely severe depression, anxiety or stress, respectively.

Patients with moderate depression were much more likely to drop out of cardiac rehabilitation (24%) than those with no or mild symptoms (13%). This was also seen in patients with anxiety (32% vs. 23%) and stress (18% vs. 10%).

About half of the patients with moderate depression or anxiety who actually completed cardiac rehabilitation did not have significant improvements in their mental health conditions.

The study was published recently in the European Journal of Preventive Cardiology.