It had been thought that any changes in personality with the drugs was due to the patient’s depression being lifted.
But now it appears the medicine, one of the drugs known as selective serotonin reuptake inhibitors or SSRIs, can directly affect traits.
The study conducted by a team at Northwestern University in Illinois, America, and published in the Archives of General Psychiatry involved randomly assigning 240 adults with major depression to receive either paroxetine, cognitive behaviour therapy or a placebo drug for one year.
Their personalities were assessed before, during and after the trial.
All experienced an improvement in their depression and after taking this into account, the people on paroxetine had a sevenfold drop in their recorded neuroticism, based on a scoring system, and a rise in their recorded extroversion by three and a half fold when compared with those on the dummy pill.
Dr Tony Tang, lead author, said: “One possibility is that the biochemical properties of SSRIs directly produce real personality change.”
People who are neurotic tend to have problems with emotional stability and can be anxious where as extroverts have more positive emotions and are socially outgoing but can be dominant.
The findings may explain why the drugs are successful in treating anxiety and eating disorders which are connected with high neuroticism and low extroversion, the authors said.