In an ideal world, research is objective and impartial. The facts are the facts, and the academic author is the objective reporter and analyzer of these facts.
In the real world that you and I live in, authors have many interests and activities to balance. For example, Doctor Chang may be a practicing physician, serve on a journal review board, receive research funding from a pharmaceutical company, and occasionally speak on behalf of a medical device company. It is natural for professionals to serve many roles in society, and having several sources of income is not prohibited. However, when the motivation of one role infringes upon the duties of another role, this can present a conflict of interest.
If Doctor Chang receives funding from Pharmaceutical Company A, he might want to, consciously or subconsciously, report favorable findings about one of Company A’s drugs. He may be encouraged to prescribe the drug to his patients, perhaps when another drug would be more effective or appropriate.
Just because Doctor Chang receives funding from Company A does not mean he will always report results that are favorable to Company A, nor does it mean he cannot research investigating Company A’s products. A conflict of interest is just the potential for misconduct: a place where extra transparency can help build trust. A conflict of interest is where human relationships, for better or worse, could affect the objectivity of research.
Conflicts of interest are a normal part of academic publishing. A reputable researcher usually has conflicts of interest to report; however, he conducts his research honestly and ethically. By disclosing conflicts of interest, especially research funding, in your journal submissions and papers, readers are alerted that research is a human endeavor, and that the research results should be examined carefully. However, there is a positive aspect too. Declaring conflicts of interest is an act of honesty: it says the author has nothing to hide, and can be trusted.
Scientific journals take conflicts of interest very seriously. Journal authors are typically required to state any conflicts of interest in a separate section when they submit manuscripts.
Sometimes this statement is as simple as “Conflicts of Interest: None”. A good sentence meaning the same thing is “The authors have no conflicts of interest to report”. See if your target journal has a preferred format for stating conflicts of interest in their Instructions for Authors page; if not, one of the options above should suffice.