Uncovering the truth about serotonin and its link to depression
Science Editor Imogen Poyntz-Wright discusses the new research behind the serotonin and depression debate.
For many decades it has been considered that depression was the result of a chemical imbalance in the brain. More specifically, caused by low levels of serotonin. Hence, today we are seeing one in six adults in England relying on antidepressants to treat the chemical imbalance causing depression, with individuals receiving mediation such as SSRIs (selective serotonin reuptake inhibitors) and SNRIs (Serotonin and norepinephrine reuptake inhibitors). In fact, SSRIs are the most commonly used anti-depressants, their role being to increase the serotonin supply in the brain.
There is no consistent evidence for serotonin imbalance causing depression.
However, new research reviewing evidence for the role of serotonin imbalance causing depression found there was no consistent evidence for serotonin imbalance in the brain being the cause of depression. In fact, research has determined that levels of serotonin in blood and brain fluids do not differ between individuals with depression and without. Furthermore, large studies found that there was no genetic difference either, with the genes of serotonin transporters not differing between people with and without depression.
However, artificially lowering serotonin levels via diet in healthy individuals had conflicting results. In the majority of studies, no link between artificially lowered serotonin levels and depression existed. Yet one study found very weak evidence for artificially lower serotonin levels in the body resulting in depression, this poor correlation was found only in 74 individuals with a family history of depression.
This new review really has called into question the usefulness of SSRIs and SNRIs. If serotonin is not the cause of depression, why are we prescribing medication that increases serotonin levels? Particularly as anti-depressants come with numerous side effects. With this in mind, there is a strong motive to focus on treatment that addresses coping with trauma or stressful life events. Further that patients should be informed that there is no known role of serotonin being the cause of depression and that anti-depressants do not address the cause of depression. This misinformation needs to be clarified to ensure patients making the decision to take anti-depressants do so with the correct knowledge.