TORONTO (Oct 3, 2005)

David Carmichael was on an anti-depressant yet in a psychotic state when he drugged and suffocated his 11-year-old epileptic son in a southern Ontario motel room.

The Toronto fitness expert was found not criminally responsible for the boy's death after an Ontario judge ruled last week that Carmichael was deluded and incapable of knowing right from wrong because he was in the grips of a crushing depression.

Carmichael's lawyer said the case illustrated the cruel yet mysterious hold a mental illness such as depression can have over even the most loving parents.

Depression and how to treat is a hot topic of debate in recent months, with even Hollywood stars weighing in: Tom Cruise and Brooke Shields sparred publicly this summer over her use of an anti-depressant to treat a severe case of post-partum depression.

Cruise says the actress was "misguided'' in her use of drugs to treat her mental disorder, and that vitamins and exercise would have been a better choice. The actor's Church of Scientology-approved tirades against anti-depressants have been making headlines and spurring discussion around the world.

The head of psychiatry at the University of Western Ontario says that while there are many well-documented benefits to anti-depressants, some patients can experience side-effects that can result in heightened anxiety.

"More severe depression is very often associated with suicidal ideas and hopelessness and desperation,'' Dr. Sandra Fisman said in an interview from London, Ont.

"If you take a medication that initially makes you feel more agitated, that may compound those symptoms that are part of depression.''

Carmichael's trial heard that he told authorities he feared his use of Paxil may have had a bearing on his behaviour. He told police after killing the boy last summer that he had started taking the drug three weeks earlier.

Court was also told he'd increased the dosage from the prescribed 40 milligrams to 60 milligrams a day without consulting his doctor.

Fisman says dosage can be crucial in counteracting severe side effects of anti-depressants, and that a thorough initial assessment of the patient's condition can help determine how much of the drug is too much.

A recent study by the University of Ottawa made some stunning links between anti-depressants and suicide among adolescents.

Researchers re-evaluated 345 anti-depressant trials for depression and other conditions involving more than 36,000 people.

They found the rate of suicide attempts was twice as high in individuals taking anti-depressants than in those using placebo pills or alternate therapy.

And now, manufacturers of the drugs are being targetted and held accountable for adverse reactions in high-profile lawsuits.

In one U.S. case against GlaxoSmithKline, the jury ruled the company's drug was largely to blame for a man's actions after he killed his wife, daughter and baby granddaughter and then committed suicide.

Dr. Henry Olders, a professor of psychiatry at McGill University, said that while he believes anti-depressants can be effective, there's no guarantee that treatment with the drugs will eliminate all symptoms of depression.

"If you talk about effectiveness, good-quality studies show anti-depressants lead to improvement in depressive symptoms in perhaps 60 to 70 per cent of properly selected patients, but actually lead to a remission of depression in typically less than 50 per cent in patients,'' he said.

"I think it's worthwhile to look for alternatives, but that doesn't mean anti-depressants are bad medication.''

While Fisman said a balance of both psychological therapy and drug treatment is key, the benefits of treating severe cases with anti-depressants over the long term outweigh potential risks of side-effects.

"The more depressive episodes that one has, the worse they get and the longer they last, so the effective treatment of an episode is important,'' she said.

"Stopping the anti-depressant (too early) likely means you have a resurgence in symptoms because the episodes aren't yet over.''