A question of health

Is there a link between mental illness and cannabis? And do genetic tests work?

DOPE-SMOKING DAUGHTER

DOPE-SMOKING DAUGHTER

Nearly all the teenagers in our neighbourhood smoke cannabis, including my 17-year-old daughter. It doesn't play a big part in her life, and I don't think it is interfering with her education. To be honest, I would rather she came home happily stoned than dead drunk. However, my oldest son (with a previous partner), who never smoked cannabis, developed mild schizophrenia in his early twenties, and I know that there are reports of a link between cannabis use and schizophrenia. Do you think a recreational cannabis user such as my daughter is more likely to develop schizophrenia than someone who does not use cannabis?

This is a question that must be in the minds of many worried parents, particularly since the Government's announcement that cannabis is being downgraded from a Class B to a Class C drug. Many tens of thousands of people have smoked cannabis without coming to any harm. The same might be said of alcohol: many people drink over decades and come to no harm. But there does appear to be a group of people who are susceptible to serious mental illnesses, such as schizophrenia. For these people, cannabis use might make the difference between a lifetime of mental health and a lifetime of mental illness. Unfortunately, we don't have any good way of identifying who is likely to develop schizophrenia. But we do know that there is a genetic element to schizophrenia, and the fact that your first son has the illness makes it a little more likely that your daughter could develop it (even though they have different mothers). Your daughter should be aware that her risks are higher than average. This should make her think twice about continuing to use cannabis.

IN THE GENES

Two of my mother's sisters have died this year from cancer, and now a cousin on my father's side has developed it. I have read about getting a genetic test to see if I am going to get cancer, and I have decided that I would like to have one. Unfortunately, my GP refuses to refer me to anyone. He says that these tests are inaccurate and unnecessary. Is it possible to have a genetic test for cancer done privately, and if so, where?

It is difficult to open a newspaper or watch the news these days without seeing something about the risks of cancer. When family members die from cancer, it is natural to wonder if there is something in the family genes that is causing it. There is a huge amount that we do not know about why people get cancer. But we do know that, for most people who get cancer, the cause is not simply a faulty gene that runs in the family. There are a few genes that can make it much more likely that you will get cancer. But even for common cancers, such as cancer of the breast and bowel, these genes are relatively unimportant for the vast majority of people. Only about 5 to 10 per cent of cancers are caused by an inherited faulty gene. When it comes to genetic tests, there is no test that will tell you whether you are going to get cancer. If a faulty gene has been discovered in someone in your family who already has cancer, it may be possible to have a test to see if you carry the same gene. If your mother's sisters were both 60 or more, your own risk of cancer is unlikely to be higher than average. Remember that cancer is a common disease - one in three people will develop cancer at some time in their lives. CancerBacup, the cancer information charity, has just published an excellent booklet that will answer most of the questions that people have about their inherited risks of cancer. It is called "Understanding cancer genetics - how cancer sometimes runs in families". You can get a copy by calling CancerBacup's helpline on 0808 800 1234; or consulting the website: www.cancerbacup.org.uk.

TABLET TROUBLE

I have recently become aware that some tablets are passing through me without dissolving. The first ones were tablets for blood pressure prescribed by the doctor. More recently, some selenium tablets seem to have gone straight through me. Does this mean that the tablets will be ineffective? Or will the active ingredients be released even if the tablets do not dissolve?

If tablets appear in the toilet bowl intact, the active ingredients will not have got into your bloodstream. There are several reasons why this may be happening. One possibility is that your intestine is overactive and things are passing through you before they get a chance to be dissolved. Or the tablets may have been manufactured in a way that makes them relatively insoluble. If so, the manufacturer needs to be told. It may be that the selenium tablets are made by a company that has failed to get the formulation right. If the problem continues, discuss it with a qualified pharmacist.

HAVE YOUR SAY: READERS WRITE

SE from London gives a timely warning about the side effects of statins:

I was very disappointed that you did not advise the patient who was taking atorvastatin to stop taking the drug because of the muscle pains he was experiencing. Muscle pains can be a sign of a potentially serious side effect. Continuing to take a statin in these circumstances can, in rare instances, lead to serious muscle problems. Statin patients who have muscle pains need a blood test to see if their muscles are being damaged.

Send questions and suggestions to: A Question of Health, 'The Independent', Independent House, 191 Marsh Wall, London E14 9RS; or fax: 020-7005 2182; or e-mail: health@independent.co.uk. Dr Kavalier regrets that he is unable to respond personally to questions