Psychology
ADHD in children: signs, diagnosis and treatment
ADHD is more than an active child. What the signs are, what else can look like it, how it is assessed, and which treatments help at each age.
27 Sept 20269 min read
Side effect
Also known as Adverse effect, Adverse drug reaction
A side effect is any effect of a medicine other than the one it was given for. Some are trivial and settle, some are the reason a medicine has to be stopped.
Medicines act on processes that exist in more than one place. A drug that blocks an enzyme in an inflamed joint blocks the same enzyme in the stomach lining — which is why an relieves pain and causes by exactly the same mechanism. Most side effects are not accidents; they are the intended action turning up somewhere it was not wanted.
Reading a side-effect list without alarm
A patient information leaflet lists everything reported during trials and afterwards, including events that may not have been caused by the drug at all. Frequencies are what make it readable: "very common" means more than one person in ten, "rare" fewer than one in a thousand. Because expectation itself produces symptoms, the arm of a trial reports side effects too, and the honest figure for a drug is the difference between the two.
A side effect is worth reporting even when it seems minor, because the alternative is often a second medicine prescribed to treat the first one's effect. Many settle within the first fortnight, and many others can be managed by changing the dose, the timing, or the drug.
Where this comes up
Psychology
Antidepressants: what they do, side effects and stopping safely
What antidepressants treat, how long they take, common side effects, whether they are addictive, and why you should never stop them suddenly.
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Psychology
Cognitive biases: the thinking shortcuts that mislead us about health
Cognitive biases are predictable errors built into normal thinking. Knowing the common ones helps you judge medicines, forwards and advice more clearly.
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Psychology
Placebo and nocebo effects: how expectations change symptoms
Expecting to feel better can ease pain and nausea; expecting side effects can cause them. Neither cures disease — and both matter in the clinic.
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Related terms
- NSAIDNon-steroidal anti-inflammatory drug, Anti-inflammatory painkillerNSAIDs are painkillers that also reduce inflammation and fever — ibuprofen, diclofenac, naproxen and aspirin among them. They work well but carry real risks to the stomach, the kidneys and the heart.
- StatinHMG-CoA reductase inhibitor, AtorvastatinStatins are medicines that lower cholesterol by reducing how much the liver makes. They are taken to lower the long-term risk of heart attack and stroke, not to treat a symptom.
- CorticosteroidSteroid, CortisoneCorticosteroids are medicines related to cortisol, the body's own stress hormone, and they are the most powerful suppressors of inflammation in general use. They are not the muscle-building steroids of the gym, which are a different class of drug entirely.
- Antibiotic resistanceAntimicrobial resistance, AMRAntibiotic resistance is what happens when bacteria change so that a medicine that used to kill them no longer does. It is driven by antibiotics being taken when they are not needed, in the wrong dose, or for too short a time, and it makes ordinary infections harder and costlier to treat.
- PlaceboDummy treatment, Placebo effectA placebo is a treatment with no active ingredient, used in trials as the comparison against which a real medicine is judged. The placebo effect is the genuine improvement people report after receiving one.
- ProphylaxisPreventive treatment, ProphylacticProphylaxis is treatment given to prevent a disease rather than to cure one. Vaccines, malaria tablets taken before travel and antibiotics given before surgery are all examples.