Patient reactions to antidepressants can vary greatly from one person to another. However, according to research from the U.S., published in the Journal of Clinical Psychiatry, depression patients also suffering from panic disorder could be prone to reporting more side effects and of greater intensity than those suffering from depression alone.

Researchers based at the University of Illinois at Chicago, U.S., studied 808 patients suffering from chronic depression and being treated with antidepressants between 2002 and 2006. Among them, 85 participants were also affected by panic disorder.

Panic disorder is an anxiety disorder characterized by recurrent panic attacks, during which the sufferer has an intense and irrational feeling of fear (sometimes fearing they might die), which can last a few minutes or several hours. Panic attack symptoms include sweating, heart palpitations, shortness of breath, chest pains, nausea and numbness. Around five to 10 per cent of the population is thought to suffer from panic attacks, with either isolated or recurrent episodes.

After 12 weeks of treatment, 88 per cent of participants reported at least one side effect.

The researchers found that participants with both depression and panic disorder were more likely to report side effects than those with depression alone, with 47 per cent vs 32 oer cent reporting gastrointestinal side effect, 26 per cent vs 14 per cent reporting cardiovascular side effects, 59 per cent vs 33 per cent reporting neurological side effects and 24 per cent vs 8 per cent reporting genital or urinary side effects.

Patients with depression and panic disorder who reported a higher number of side effects were also more likely to report a worsening of their depression, the study found.

However, the scientists found no significant increase in side effects affecting eyes, ears, skin, sleep or sexual function.

"People with panic disorder are especially sensitive to changes in their bodies," said Stewart Shankman, professor of psychology and psychiatry at UIC and corresponding author on the paper. "It's called 'interoceptive awareness.'

This hypersensitivity could logically explain the greater likelihood of such patients reporting psychological side effects of their treatment.

As a result, the researchers advise medical professionals to carefully investigate reported side effects to establish which may be due to hypersensitivity before considering adjusting medication doses or switching treatments.