Serotonin and Depression

Question 1

Define Melancholia

Answer 1

The excess of black bile (Hippocrates)

Question 2

DSM-5 Depression Symptoms

Answer 2

Low mood and loss of interest of pleasure (anhedonia)

Additional symptoms (2+ weeks)
1. Weight loss/gain
2. Slowing down of thoughts/movement
3. Fatigue/less of energy
4. Feelings of worthlessness/excessive guilt
5. Difficulties with concentration/indecisiveness
6. Suicidal thoughts

Question 3

Define Serotonin

Answer 3

Neurotransmitter associated with sleep, mood, anxiety, sexual behaviour, serotonin nuclei (raphe) located in the midbrain and stem

Question 4

Define SSRIs

Answer 4

Selective Serotonin Reuptake Inhibitors

First line pharmacological treatment for depression. A class of antidepressants that INCREASE 5-ht concentrations. SSRIs BLOCK 5-ht transporters preventing them from clearing 5-HT from the synaptic cleft

Question 5

Monoamine hypothesis of depression

Answer 5

Suggested by Schildkraut (1965)

Depression is caused by a REDUCTION in…
1. Serotonin
2. Dopamine
3. Norepinephrine

Evidence that SSRIs improve depression relative to placebo

Question 6

Evaluate SSRIs

Answer 6

Indirect relationship (just because SSRIs improve depression does not mean a lack of serotonin CAUSES depression)

Delayed onset of therapeutic benefits despite quick blockade of 5-HT transporters (e.g. Harmer et al, 2009; Kohler et al, 2016)

SSRIs not effective for everyone (Nutt, 2007)

Serotonin theory is widely debated (Moncrieff et al, 2022)