We have a grandson who was diagnosed with attention deficit hyperactivity disorder (ADHD) at the age of five, and our daughter feels guilty that it may have been her fault. Is it inherited or environmental?
Please try to assuage her guilt. Current estimates for the UK are that about 4% of boys and just under 1% of girls aged five to 15 years old have been labelled as having ADHD. We don't know why boys are more susceptible than girls. Inheritance plays a part and other risks add to the possibility that it will develop, such as an injury in the early years, maternal smoking and drinking, maternal heroin use in pregnancy, relative lack of oxygen at birth, and even zinc deficiency. However, in most cases there is no discernible cause - so your daughter mustn't feel it's her fault.
My father takes ginkgo biloba because he says it 'helps his brain' and could prevent Alzheimer's disease. Is this correct? If so, when should I start taking it?
I'm sorry to disappoint you and your father, but there's no evidence that it makes a difference to the brain. Ginkgo was proposed as a brain 'protector' because it contains 'flavonoids' and 'ginkgolides' that seemed to protect against nerve deterioration in laboratory tests, so it is widely promoted for that purpose. However, a study of more than 3,000 Americans of 75 and over, with no dementia when they started the drug or the placebo, found no difference between the two groups in their subsequent dementia rates. In fact, in one subgroup - people with circulation disorders - there was more dementia in the ginkgo group. So don't bother starting, although whether you tell your father this is up to you.
When I trained as a nurse (too many years ago), I was told high blood pressure isn't as damaging for a woman as a man, and that lowering it didn't make much difference in the long term. Is that right? Are we protected by our hormones?
That's a fallacy that was exploded a few years ago. It's true women tend to have heart attacks and strokes, on average, a decade older than men do, but high blood pressure is as lethal to them and they get just as much benefit as men do (in lowering death and serious disease rates) from treatment to lower it to normal levels. So if you are writing about yourself, please go on taking the tablets.
• Do you have a question for Dr Smith? Email: doctordoctor@theguardian.com
