In the earlier University of Hull study researchers accepted that many people do feel the effects of the drugs, but they argue that it could be a placebo effect. People feel better only because they are taking medication they feel will help them. Researchers focused on drugs which work by increasing levels of the mood controlling chemical serotonin in the brain.
The researchers found that the effect of the drugs were no better than those achieved by giving patients a sugar pill. They concluded that the drug-placebo differences in antidepressant efficacy increase as a function of baseline severity, but are still relatively small even for severely depressed patients.
The relationship between initial severity and antidepressant efficacy is not attributed to increased responsiveness to medication but rather to decreased responsiveness to placebo among very severely depressed patients.
The President of the American Psychiatric Association said she wasn't surprised that the study found that not every antidepressant works for everyone. She states, "Medication helps some, but not all, people with depression. For people with mild to moderate depression, psychotherapy can work as well as medication. Studies have shown that between 70 to 80 percent of people can and do get better with a combination of treatment approaches, which will often include individual therapy, family therapy and/or medication."
The newer study clouds the assumptions even further. Previously the common assumption was that personality changes during SSRI treatment occur only as a byproduct of alleviating depressive symptoms. In this study, the advantage of SSRI treatment over placebo in changing personality appears far more drastic than its advantage over placebo in alleviating depression.
For those patients who had the most dramatic relief from depressive symptoms after taking the SSRI mediation were the least likely to relapse.
The researchers elaborated suggesting that as depressive symptoms were alleviated patients were able to learn cognitive therapy strategies that helped them to maintain relief and ultimately resulted in long-term positive effects.