Practices

Put an actual number on it: how many coffees, teas, energy drinks and colas in a normal day. Without that number, your sleep problems, your anxiety and how well a medication is working are all being read against an unknown.

People underestimate this, partly because it feels embarrassing and partly because a large takeaway cup is often two or three servings. Count across…

Stimulants sharpen focus in almost anyone, so responding well to one does not confirm you have ADHD. The diagnosis comes from your history and how you function, not from a trial of tablets.

This cuts both ways. Someone can be handed a diagnosis on the strength of a good response, and someone else can be doubted because their response was…

If you are testing whether a food affects you or your child, the test has to be complete. Among children with suspected sensitivity to artificial colouring, most reacted to as little as 100 mg, so a bit left in is enough to blur the answer.

What usually happens is that a family removes the obvious sources, misses the ones hidden in medicines, sauces and cereals, sees no change, and…

If you are going to test whether a food matters, work out in advance where the plan will leak. School lunch swaps, a grandparent's biscuit tin, your own memory on a hard week: all of it decides whether the answer means anything.

Change one thing at a time and keep everything else steady, otherwise you cannot tell which change did what. Then be honest about who is running the…