A study just released in the Archives of General Psychiatry has found that the prescription of multiple psychiatric drugs to individual patients has increased greatly in recent years despite their being little hard evidence about the benefits and risks of combining medication.
The practice of prescribing multiple drugs is called ‘polypharmacy‘ and usually occurs because a single medication doesn’t treat the symptoms adequately or quickly enough.
This situation is common in psychiatry partly due to what is euphemistically known as ‘treatment resistance’. This phrase is often used as if the patient has an especially tough case of the disorder (e.g. they have ‘treatment resistant schizophrenia’) or if it is a biological trait of the person (the patient is ‘treatment resistant’) but it could equally well describe the fact that the drugs don’t work very well – or rather, they don’t work very well for everyone.
This is common enough that in schizophrenia, about a third of patients show little or no response to common antipsychotic drugs and many of the rest don’t have their symptoms completely controlled. There are similar numbers in people with depression.
It may also be the case that a patient has other symptoms, severe anxiety for example, and in any of these cases the psychiatrist will often add medications on top of each other, attempting to improve the outcome.
However, there is very little research on medication combinations. We have some studies that show that adding one drug to another (‘augmenting’ in the jargon) can improve outcome with some drugs and in some conditions, but these are few and far between.
There is virtually no good quality evidence on the effects of three or more drugs, but this is exactly where the rates of prescribing have risen, as shown by the most recent study which looked at how common this was in US office-based (rather than on hospital ward) consultations with a psychiatrist:
Between 1996 and 2006, there was a substantial increase in the proportion of patient visits in which 2 or more psychotropic medications were prescribed. During this period, the proportion of visits in which 3 or more psychotropic medications were prescribed increased from fewer than 1 in 5 to nearly 1 in 3.
One of the reasons there are so few trials of medication combinations is that drug companies are reluctant to fund them, given that they would rarely include two in-patent medications from the same company, meaning they could use the results to promote their products.
This has meant that we have had to wait until quite recently for, for example, the results of the US government funded STAR*D study on depression treatment to find out whether some combinations actually help.
Link to study on increase in polypharmacy in psychiatry.