Lecture 4: Depression Flashcards
Which neurotransmitter is thought to play a major role in depression? How did this theory came up? What is the recent view on this topic?
The serotonin hypothesis is based on a study (more than 50 years ago) that could show that depression was related to a deficiency in tryptophan, a precursor of serotonin. Nowadays, researchers think of serotonin levels as playing a role in maintaining depression (but not causing it).
Which personality characteristics are related to depression?
High neuroticism, low extraversion and low conscientiousness.
What is the amount of heritability of depression?
35%.
Which brain areas are related to depression?
Prefrontal cortex, hippocampus and amygdala.
How does the prevalence of depression develop over life time?
In < 18 years fairly low prevalence (1-4%), from 18-60 years significantly higher prevalence (18%) and even higher prevalence in 60+ years (20%).
Name the main factors involved in developing depression with reference to the age groups < 18, 18-60 and 60+ years.
< 18: prenatal, genetic and brain related factors. 18-60: stress and hormones. 60+: brain, cardiovascular and metabolic factors.
How does depression influence the risk of dementia?
Depressed people have a two-fold increased risk for dementia. However, the causal relationship is unclear.
What are the three main hypotheses regarding the relationship between depression and dementia?
1) Glucocorticoid cascade hypothesis -> aging + stress = neurodegeneration
2) Vascular risk hypothesis
- > aging +depression = vascular damage -> dementia
3) A common factor causing both LLD and dementia
Describe the stress-response system.
The hypothalamus acts upon the pituitary glands via corticotropin-releasing hormone (CRH) which in turn release adrenocorticotropic hormone (ACTH). ACTH acts upon the adrenal gland, which releases cortisol. Finally, the hypothalamus responds to the level of cortisol.
Describe the glucocorticoid cascade hypothesis in detail.
The stress response acts upon the HPA axis, leading to higher release of glucocorticoids (cortisol) which affect function and structure of the hippocampus. Impairments in the anterior ventral hippocampus are related to depression while impairment of the posterior dorsal hippocampus is related to dementia. (In addition the anterior ventral hippocampus affects the posterior dorsal hippocampus).
Regarding the hippocampal and entorhinal brain volume, how do early-onset and late-onset depression differ?
The mean hippocampal volume is smaller in early-onset depression (however, not significant!). In late-onset depression the entorhinal cortex is smaller (not significant).
Describe the vascular risk hypothesis in detail.
Depression leads to vascular problems. Hypertension, vascular risk factors or cardiovascular disease lead to stroke, small vessel disease (SV) or β-amyloids. Stroke and SV can lead to vascular cognitive impairment, which in turn can lead to vascular dementia or Alzheimer’s disease. The β-amyloids can lead to neurodegenerative brain lesion in turn leading to dementia.
