Are antidepressants over-prescribed?

Antidepressant use continues to rise yet the jury is still out on the drugs' effectiveness for the most common forms of depression, writes Scientia Professor Philip Mitchell.

Antidressants Mitchell cropped

The use of antidepressants in developed countries is increasing in the range of between 6% and 9% annually.

The British Medical Journal (BMJ) has just published two opposing views on the vexed question of whether antidepressants are being over-prescribed. The issues raised by debate are by no means unique to the United Kingdom; increasing rates of antidepressant prescribing are apparent in most developed countries, including Australia.

The BMJ discussion was precipitated by recent UK prescribing data, which reported a 9.6% increase in antidepressant prescriptions in 2011 – the largest increase in prescriptions of all medication classes for that year.

Arguing that the figures indicated over-prescribing, general practitioner Des Spence writes, “I think that we use antidepressants too easily, for too long, and that they are effective for few people (if at all)."

In the opposing camp, professor of psychiatry Ian Reid contends, “Given recent demonstrations that depression is still under-recognised and under-treated, the claim that antidepressants are over-prescribed needs careful consideration.”

Situation in Australia

recent report on prescribing patterns of antidepressants and other psychotropic medications (drugs for mental illnesses) has aroused similar controversy in the local media. The study’s authors reported a 58.2% increase in the dispensing of psychotropic drugs over the period from 2000 to 2011, including a 95.3% increase in antidepressants.

Echoing the argument that antidepressants are being over-prescribed, the authors raised concern about “ … the dramatic increase in antidepressant prescriptions despite questions about the efficacy of these drugs in mild to moderate depression."

These recent UK and Australian data are not surprising; they are consistent with the major increase in antidepressant prescribing that’s been occurring in most developed countries since the introduction of the SSRI (selective serotonin reuptake inhibitor) antidepressants in the late 1980s and early 1990s.

An international trend

In 2000, my colleagues and I wrote one of the first major reports of this global trend. We found an approximately threefold increase in antidepressant prescribing in Australia from 1990 to 1998. The increase reflected what was occurring in most major Western countries and coincided with the widespread introduction of SSRI antidepressants such as Prozac, Zoloft, Aropax and Cipramil during that period.

In a another paper, we examined a longer timeframe (1975 to 2002) finding a 1.1% annual increase in antidepressant prescribing from 1975 to 1990, an acceleration to 29% in 1995, then a slowing down to 6.6% in 2002.

There’s no doubt there’s a continuing increase in the use of antidepressants in developed countries such as Australia and the UK, in the range of between 6% and 9% annually. The critical question, though, is whether this substantial increase in prescribing is justified at both a national public health and the individual clinical level.

Benefit or harm?

In Australia, we are able to look at the question of benefit or harm by examining national epidemiological and suicide data.

In terms of adequacy of depression treatment, a 2007 national survey found that 6.2% of individuals had experienced a mood disorder (mainly depression) over the prior 12 months, but over half (51.2%) did not access any services for mental health problems in that time. This indicates a substantial unmet treatment need for depression, rather than over-treatment.

While it’s not possible to identify rates of antidepressant prescribing, as such, from the survey, the rate of use for psychological services was 23.2% for those with a mood disorder. This is a substantial increase from the 11.8% in an analogous 1997 survey, suggesting that doctors were readily utilising psychological services via Commonwealth-funded schemes such as Better Access.

Overall, these data do not indicate that there’s over-prescribing of antidepressants in Australia.

Antidepressants and suicide

A second potential measure of the value or otherwise of this increase in antidepressant use is its impact on suicide rates.

We examined this question in 2003, and found there was a significant correlation between changes in antidepressant prescribing rates from 1991 to 2000 and the rates of suicide. We also found that people in age and gender groups with increased rates of prescribing demonstrating lower suicide rates.

This same finding has also been reported in the United States and Scandinavia, indicating that greater rates of effective treatment for depression in a population have a significant impact on suicide.

We interpreted our findings broadly – that effective treatment of depression, whether by medication or psychological treatment can lead to a measurable benefit (here a fall in suicide rates), even at a whole population level.

Issues around effectiveness

Another issue raised in the BMJ debate is the current state of knowledge about the effectiveness of antidepressants for those with mild depression – the most common form in the community. Unfortunately, current evidence is inconsistent and dependent on the methodology used by researchers.

A highly publicised 2008 meta-analysis of published and unpublished antidepressant trials found that only those with severe levels of depression benefited more from antidepressants than a placebo.

But a recent report examining longitudinal data from individual patients in a series of large antidepressant trials found no relationship between likelihood of benefit from antidepressants and the initial severity of depression. In other words, patients benefited at similar rates independently of how severely depressed they were.

These inconsistent findings indicate the jury is still out on whether those with mild depression benefit from antidepressants.

What to make of it all?

So, where does this leave us in determining whether current rates of antidepressant prescribing are excessive? While rates of prescribing are undoubtedly increasing, data from national surveys suggest continuing high rates of untreated depression as well as increased use of psychological services. And, as discussed above, findings from a number of developed countries, including Australia, indicate the public health benefit of reduced suicide rates.

Still, we must remain vigilant in monitoring such prescribing and avoid mindless use of antidepressants, particularly for milder levels of depression where psychological treatments are probably more appropriate.

Scientia Professor Philip Mitchell is the Head of  the School of Psychiatry at UNSW.

This article was first published in The Conversation.

If you think you may be experiencing depression or another mental health problem, please contact your general practitioner or in Australia, contact Lifeline 13 11 14 for support, beyondblue 1300 22 4636 or SANE Australia for information.