There is evidence that research studies sponsored by pharmaceutical companies produce biased results. Here is a collection of papers supporting this claim:
This paper from the American Journal of Psychiatry reports that industry-sponsored studies are 4.9 times more likely to show a benefit for their product.
In this paper, an association is shown between industry involvement in a study, and the study showing a larger benefit for the industry's product (in this case, with newer antipsychotics).
In this study, the findings suggest that the direct involvement of a drug company employee in the authorship of a study leads to a higher likelihood of the study reporting a favourable outcome for the drug company product.
This is a very important JAMA article, showing that industry-funded studies are more likely to recommend the experimental treatment (i.e. favouring their product) than non-industry studies, even when the data are the same.
I do not publish this post to be "anti-drug company". I think the pharmaceutical industry is wonderful. The wealth of many of these companies may allow them to do very difficult, hi-tech research with the help of some of the world's best scientists. The industry has produced many drugs that have vastly improved people's lives, and that have saved many lives.
Even the profit-driven-ness of companies can be understandable and healthy...it may lead to economic pressure to produce treatments that are actually effective, and that are superior to the products of the competitors.
Sometimes the research trials necessary to show the benefit of newer treatments require such a large scale that they are very expensive...sometimes only a large drug company actually has enough money to sponsor trials of this type.
BUT...the profit-driven orientation of companies may cause them to take short-cuts to maximize profits...
-marketing efforts can distort the facts about effectiveness of a new treatment
-and involvement in comparative trials by eager, profit-driven industry, very likely biases results, and biases the clinical behaviour of doctors
A solution to some of these problems is a requirement for frank transparency always, when publishing research papers, in terms of industry involvement.
Another solution is to have more government funding for independent, unbiased large-scale clinical trials.
And another solution is for all of us to be better informed about this issue!