For a condition as complex, poorly understood and stigmatised as depression, it should come as no surprise that one of the major treatments – antidepressants – suffers the same problems.

Those who are most likely to benefit are often reluctant to take antidepressants, while those less likely to benefit are often given them due to a lack of more suitable alternatives.

One thing is clear – we are taking antidepressants in greater quantities than ever before. A 2013 OECD report showed Australia to be second-biggest consumer of antidepressants in the OECD, second only to Iceland, with 89 adults per 1000 taking the drugs compared to 71 in the United Kingdom, and an average of 56 across all OECD nations.

Between 2000 and 2011, antidepressant use in Australia increased by a staggering 95.3 per cent, according to one study.

Yet there is also evidence that depression is undertreated. A 2009 survey found only around one-third of people who met the criteria for a mental disorder made use of mental health services.

For the ‘right type’ of depression

Part of the problem is depression is a complex condition, ranging in severity, cause, biochemistry and outcome. Antidepressants work very well for some people, but for others they may be ineffective, so there cannot be a one-size-fits-all treatment approach, says Dr Jan Orman, a GP at the University of Sydney and GP Services consultant for the Black Dog Institute.

“Antidepressants are great if the patient has the right kind of depression or if their anxiety is disabling them, because antidepressants work very well in both those situations,” says Ormand.

The ‘right’ kind of depression is generally melancholic depression, as opposed to non-melancholic depression. In melancholic depression, according to the Black Dog Institute, physical and biological factors play a much bigger role whereas in non-melancholic depression, personality and life stressors contribute much more to the depression. This distinction has important implications for treatment, says Orman.

“We know that of the non-melancholic sort, 90 per cent of people who come to their GP with depression have the non-melancholic sort and we know that only half of those are going to respond to antidepressants,” she says.

“On the other hand, the 10 per cent of people who have melancholic depression really do respond well to antidepressants.”

However, the evidence suggests most prescriptions for antidepressants are written by general practitioners, who are also much more likely to be treating those with non-melancholic depression – the kind that responds much better to non-pharmacological therapies like cognitive behavioural therapy.

Unfortunately, there is considerable pressure on GPs to prescribe antidepressants, says Orman, particularly because, despite recent initiatives around mental health, there is still a shortage of psychology and psychiatry services.

“It’s always easier, under pressure from a distressed patient, to provide a prescription… and the pressure to prescribe on GPs is enormous,” she says.

“They don’t necessarily know when is the most appropriate time to prescribe and when perhaps they should be using other techniques, and they don’t necessarily have other techniques at their disposal.”

Treatment opportunities missed

The flip side of the coin is that those who do need antidepressants and will most likely respond well to them are not getting them, says psychiatrist Dr Samuel Harvey.

“We have repeated studies showing that overall depression and anxiety are disorders that are still under-treated in the community – lots of people with depression or anxiety don’t get appropriate treatment,” says Harvey, senior lecturer at the University of NSW and the Black Dog Institute.

“It’s a shame because … there are few cases where you see people’s lives turn around so dramatically as if you’ve got somebody whose life has been blighted by depression or anxiety and sometimes, when you get them on the right antidepressant the change is remarkable.”

The reason for this under-treatment is often due to an individual’s own reluctance to take antidepressants.

“A lot of people worry that this is addictive, that it will change their personality, that it will turn them into a zombie, that it’s an admission of failure if they’re needing to take antidepressants,” says Harvey. “I hear these things a lot in the clinical setting.”

Concerns over side effects

Antidepressants also have a bad reputation because of people’s concerns over their side effects.

Orman says most people will have some side effects within the first few days of starting treatment, but that these are mostly short-term and can be managed.

“The side effects that I generally mention are headache, nausea, sleep disturbance. I provide them with information about what to do about those things like take panadol for headache, take them with something in your stomach if they give you nausea, take them early in the day if they disturb your sleep,” says Orman.

“Those side effects settle down and if they don’t settle down then it’s probably not the right drug for them and they need a different drug.”

Sexual side effects are known to occur with some types of antidepressants, and sometimes they can also interfere with bowel function. However, Orman says the issue of weight gain is a myth, as research has found only one of the newer types of antidepressants has been associated with this.

Suicide risk

Another common concern about antidepressants is whether they increase the risk of suicide in the first few weeks after starting therapy.

Harvey says there is some evidence, particularly in adolescents and young adults, of an increased risk of suicidal thoughts and acts in the early period after starting a course of antidepressants.

“The group we’re looking at are the group that are at their most depressed, who are in that period of waiting for the antidepressant effect to kick in so it’s not surprising that there would be some increase in suicidal thoughts and acts during that time,” Harvey says.

Some people also get a slight increase in agitation when they start on antidepressants, which can contribute, but closer monitoring is now recommended for the first couple of weeks after treatment begins.

Ultimately, Harvey says the best outcome is to ensure people get treatment for their depression.

“The message we’re still trying to get out there is if we want to stop people killing themselves, the best way to do that is to diagnose and treat their depression.”

This article first appeared on ‘ABC’ on 18 September 2014.