That doesn't necessarily mean that the studies, methodology, and/or conclusions are wrong. Who do you think funds the vast majority of studies on oil? or sugar? Yea, the oil industry and the food industry. As a Materials scientist myself, I, and my advisors in the past, have submitted grant proposals to, for example, carry out research on the properties of bitumen, a product of the oil industry. If I had received that funding, and published that research, does that automatically make me a shill of the oil industry? Does taking money from the oil industry invalidate my work and my results?

It isn't as black and white as 'where does the money come from'. It is no surprise that drug studies are funded by the pharmaceutical industry. They are the ones most interested in drug effects. There isn't some grand conspiracy here.

Of course, with all that being said, I am not saying that the funding source never matters. There are definitely concerns about conflict of interest, but I think that the integrity of the scientist through their past research output and quality of work should be the first thing to look at if one is concerned about fudging results or what-have-you.