They found that increasing serotonin made individuals better able to control their behaviour, particularly when exposed to negative information. The study also showed that elevated serotonin levels benefited different types of memory. Unlike traditional techniques, this novel drug directly increases serotonin levels in the human brain. 'This provides us with some exciting new information about the role of serotonin in humans. This study helps to further understand why drugs that change serotonin levels are effective treatments for many mental illnesses, including depression, anxiety and obsessive-compulsive disorder.'