Affective disorders: Neurobiology and treatment Flashcards
Factors - neurobiology of major depression
- Adverse childhood experience
- Current stress
- Genetic factors
–> Decrease in 5HT and NA function
How do adverse childhood experience, current stress and genetic factors cause a decrease in 5HT and NA function
HPA axis function –> Cortisol –> 5HT and NA function
Aetiology of depression
- Multifactorial
- Incompletely understood
- Interactions of genetic factors, childhood adversities, past hx of mood disorders, psychological predisposition (neuroticism)
- Often precipitated by stressful life events
Monoamine dysfunction in depression
- All traditional antidepressants affect 5-HT/NA systems
First MAOi
- Iproniazid
First tricyclic
- Imipramine
What type of receptor is reduced in depression
- Reduced 5-HT transporter in depression
Where are 5-HT cell bodies located
- raphe nuclei
Where are NA cells located in a large cluster
- Locus coeruleus
What are the raphe nuclei and locus coeruleus believed to be involved in
- Each of these midbrain nuclei has ascending tracts, which project to brain regions thought to be involved in depressive symptoms, as well as ascending and descending tracts involved in pain suppression
What is the monoamine theory of depression
- Suggests that a relative deficiency in synaptic levels of serotonin and noradrenaline in key central nervous system pathways underlies depressive illness (CNS = brain + spinal cord)
Where do 5-HT and NA- secreting neurons project
- Project upward from their respective nuclei in the brainstem, directly stimulating many areas of the brain
What brain areas are stimulated by 5-HT and NA
- Prefrontal cortex, which is involved in executive functions, and the limbic system which include anatomical structures involved in behaviour, motivation, and emotion, such as the hippocampus, anterior cingulate cortex, hypothalamus, and amygdala
1st generation antidepressants
- MAOi - Phenelzine, tranylcypromine
- Tricyclic antidepressants - Amytryptiline, clomipramine
Action of MAOi
- Nonselectively inhibit enzymes involved in the breakdown of monoamines, including serotonin, dopamine, and norepinephrine
Action of tricyclic antidepressants
- Nonselectively inhibit the reuptake of monoamines, including serotonin, dopamine, and norepinephrine
2nd generation antidepressants
• SSRI: Selective serotonin reuptake inhibitors
Sertraline, Citalopram, Escitalopram, Fluoxetine
• SNRI: Serotonin-noradrenaline reuptake inhibitors
Venlafaxine, Duloxetine
• alpha2 and 5-HT2 antagonist [modulate serotonin and NA release]
Mirtazapine
• Dopamine-noradrenaline reuptake inhibitor
Bupropion (not approved as antidepressant in UK)
Efficacy comparison - SSRIs and tricyclics
- Equal in outpatients
Spectrum of action - SSRIs
- Large spectrum of action
- OCD, PTSD, Panic, GAD, social anxiety
Toxicity of SSRIs
- Low toxicity and safe in oversdose
Initial treatment phase of SSRIs
- Initial treatment phase is the most delicate, due to prevalence of side effects over benefits - Slow titration
Side effects of SSRIs
- Gastro-intestinal symptoms(nausea, diarrhoea)
- Headache, irritability, anxiety
- Reduction of libido and sexual dysfunction