According to the findings of a recent study led by Dr Rene Hen, from Columbia University in New York and a researcher at the New York State Psychiatric Institute, the reason why half of the people who have been prescribed antidepressants fail to benefit from them is that their brain resists the drugs.

The researchers said that most antidepressant “sunshine” pills work by increasing levels of a brain chemical called serotonin or “happiness chemical” – which is a neurotransmitter that facilitates the message-passing process between nerve cells. However, in nearly one-half of the people who are given antidepressants, the pills end up lowering the brain’s serotonin level, rather than raising them.

Noting that the certain molecular differences in brain make-up are largely responsible for the effectiveness or otherwise of the antidepressants, Hen elaborated: “The more antidepressants try to increase serotonin production, the less serotonin they actually produce.”

The research was undertaken on a genetically-engineered mouse, programmable for serotonin neurons with high or low numbers of the molecules; and it was found that the level of success of the antidepressants, similar to the success rate in humans, was almost 50 percent.

Despite the fact that the researchers studied the effect of antidepressants on mice, it is believed that the findings would be applicable to humans as well, with surplus 1A-type receptors supposedly leading to failure of antidepressant treatment in some people.