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No clear link between low serotonin and depression

An important international study found no clear evidence that low levels of serotonin are responsible for depression.

Researchers are now questioning New Zealand’s reliance on serotonin-targeting antidepressants, as drug prescriptions have increased dramatically in recent decades, while other forms of mental health services have increasingly become rarer.

For many physicians, antidepressants are the primary tool for treating depressive disorders, with most forms of medication targeting serotonin, often dubbed the “happiness” neurotransmitter.

READ MORE: 40% of New Zealand children showing signs of depression during lockdown – study

But new research, spanning multiple studies involving tens of thousands of people, has so far found no evidence linking depression and low serotonin.

Clinical psychologist Dougal Sutherland says the results aren’t completely shocking.

“In a way it was a surprise like ‘man, there’s no evidence at all’, and in another way it kind of confirmed what we already knew.

“People with depression, a lot has happened in their lives and trying to simplify it to a chemical imbalance in the brain seems like an oversimplification.

“You’re taking antidepressants now and they work for you, I would say keep taking them…but the problem with that is that we know antidepressants only work for some.”

GP Dr Bruce Arroll says these drugs are not always effective and are often used as first line of treatment by doctors, rather than as a last resort.

“Antidepressants really only work on the severe end of the spectrum…about 12%-13% of New Zealanders take antidepressants, but only 2%-3% get a chemical benefit.

“Traditionally, antidepressants have been used a lot…I think for some prescribers it can be seen as an easy fix and it gets the patient out the door quickly.

“They shouldn’t get it on the first visit, basically you should give people exercise, contact friends and do something enjoyable.”

“If it doesn’t work after 2 or 3 weeks, you might want to talk about medication.”

The distribution of antidepressants in New Zealand is on the rise, data from the Ministry of Health shows that prescriptions have increased by 20% in 2020 compared to 2010.

Arroll says the new research doesn’t mean giving up on pills, but rather that the healthcare system should make available a range of alternative treatments such as talk therapy.

“It’s a longer-term question of where to redirect resources and how to actually help…and it may not be about putting more money into drugs.”