Pharmaceutical industry revenues from global pharmaceutical sales have increased 7% to $602 billion in 2005. Approximately 15% of these revenues were spent on clinical research and drug development studies. Because of the huge budget allocated to research and development studies the number of studies being conducted by pharmaceutical companies has increased. The impact of the pharmaceutical industry on clinical trials has been affected by financial conflicts of interest between researchers and the industry.

Conflict of interest refers to a situation in which it appears that a researcher's personal financial interest could significantly affect the design, conduct, and/or reporting of such research. Financial conflict of interest has been reported to be frequent in clinical trials in general medicine. It is estimated that 89%-98% of comparative drug treatment studies are funded by pharmaceutical companies. It was reported that favorable outcomes for the firms conducting these studies were significantly more common in industry-funded studies than in non-industry funded ones. These biased outcomes were due to conscious or unconscious decisions about the design, data analysis, and publishing of the studies.

Biased outcomes of industry-funded studies have diminished the integrity of academic institutions, pharmaceutical companies, researchers, and scientific journals; therefore, various precautions have been taken in order to reduce the effect of conflict of interest on study outcomes. The aim of this review was to evaluate the effect of conflict of interest on outcomes in clinical psychiatry studies.