Expectation of treatment side effects is consistently linked with those symptoms being realised. Patient expectations, including those generated by the informed consent process, can have a large influence on the side effects that patients feel after starting a new medical treatment. Such symptoms may be the result of the nocebo effect, whereby the expectation of side effects leads to them being experienced. Side effects may also be due to the misattribution of pre-existing or unrelated symptoms to the new medication. Medical professionals’ own negative beliefs about a treatment, especially generic drugs, may further enhance patients’ expectations of adverse effects. The news media may also influence expectations, particularly when media attention is directed towards a health or medication scare. This field of research has ethical and clinical implications for both medical professionals and the news media with respect to the level and type of information about treatment side effects that is provided to patients or members of the public.