It may sound weird, but I tell my patients not to read about side effects of medicines on the papers or pamphlets that come with the pills, or that can be found on the internet. This is not because I want to hide anything, but rather because the lists can be highly inaccurate and misleading. Here’s why.
Drug companies are required to list any side effect experienced by somebody taking the medication, even if there’s no evidence that the medicine caused it. If somebody in a study had a headache, then “headache” winds up in the list. I’ve occasionally seen “car accident” listed. There’s evidence that the more a person reads about all the side effects, the more likely they are to experience them. This effect is called “nocebo,” the opposite of “placebo” (see link).
Sometimes side effects are listed as “occurred in over 10% of people,” “occurred in 5-10%,” “occurred in under 1%,” etc. Still, that doesn’t mean the more frequent ones are due to the medication, because there’s no information given about who in the study got side effects on placebo (a dummy pill). If 10% of people taking the medication and also 10% of those taking placebo got a headache, the “10%” tells us nothing.
It can be tricky to determine if a medication is causing a certain symptom. Sometimes it’s the disease for which the med was given that’s responsible. Symptoms like nausea and dizziness are so common that it’s almost impossible to know if it’s the medication. But some meds are notorious for causing a specific symptom, so if that occurs, the drug is likely the cause.
I’ve seen patients stop taking important, even life-saving, medications because they thought it was causing a certain symptom. Before doing so, it’s always better to discuss it with whoever gave you the med. We may well substitute another type of drug if possible. Or sometimes we advise to stop the med for a month, then try it again (called a “rechallenge”). If the side effect goes away, then happens again on rechallenge, we’re more convinced that the drug was the cause.