Depression causes gray matter in the brain to decrease. This is important to keep in mind when looking at studies of trans people’s brains as many trans people have experienced depression.
These are just a few links to studies looking at depression’s effects on the brain. A smaller hippocampus seems to be particularly related to depression, although studies have also found a link to an overall decrease in gray matter.
The bottom line is that studies of gray matter and gender identity need to take into account past and present depression in both trans people and controls.
For anyone with depression, the bad news is that it’s not good for your brain. The good news is that you can do things for your brain – exercise, meditate, and learn.
You may be able increase the volume of your hippocampus with regular exercise. Eight weeks of mindfulness meditation increases the volume of your hippocampus and may increase the gray matter volume in other areas of your brain as well. You can increase your gray matter by learning a new skill like juggling or by reading text written backwards. Going to medical school affects your gray matter.
Back to the studies and the link between gray matter volume and depression.
This study found that patients who were currently depressed had lower volumes of gray matter in the hippocampus compared to both healthy controls and people who had had depression before but were not currently depressed. After taking citalopram, the patients with current depression had more gray matter in the hippocampus.
This study found that patients with major depressive disorder had “a strong gray-matter reduction in the right anterior insula. In addition, region-of-interest analyses revealed significant gray-matter reductions in the hippocampal formation.”
The effects were stronger for people who had had more episodes of depression than people who had only had one episode.
The more episodes of depression a patient had, the less gray-matter volume they had in the right hippocampus and right amygdala.
“The anterior insula gray matter structure appears to be strongly affected in major depressive disorder and might play an important role in the neurobiology of depression. The hippocampal and amygdala volume loss cumulating with the number of episodes might be explained either by repeated neurotoxic stress or alternatively by higher relapse rates in patients showing hippocampal atrophy.”
In other words, having depression might affect the hippocampus or having a small hippocampus might make you get depressed more often.
This study found that the more months the patients had spent being depressed, the less total cerebral gray matter they had. More months of depression was also linked to less frontal gray matter, less temporal gray matter, and less parietal gray matter. The study only included female patients who had recurrent depression. They did not control for the anti-depressants the patients used, so it is possible that the medicines affected their gray matter.
This study looked at people who don’t have depression but who might be vulnerable to it. The “cognitively vulnerable” group was chosen by their answers to two questionnaires. The first questionnaire looked at thinking styles that may contribute to depression – people may be vulnerable to depression based on how they think about causal attributions, consequences, and self-worth characteristics. The second questionnaire asked about symptoms of depression.
Cognitively vulnerable people had less gray matter volume in the left precentral gyrus and right fusiform gyrus compared to controls. In addition their right fusiform gyrus and right thalamus were smaller compared to people who had major depressive disorder. Patients with major depressive disorder had reduced gray matter volume in the left precentral gyrus and increased gray matter volume in the right thalamus.
“Reductions in brain gray matter volume exist widely in individuals with CVD. In addition, there exist similar abnormalities in gray matter volume in both CVD subjects and MDD patients. Reductions of gray matter volume in the left precentral gyrus might be correlated to the negative cognitive styles, as well as an increased risk for depression.”
Of course, we don’t know which way the causality goes – is the cognitive style causing a lower gray matter volume in the left precentral gyrus or is the lower volume of gray matter causing the cognitive style?
This study found that people with major depressive disorder had 4.4% less global gray matter volume than controls. This would be the decrease expected in 14 years of normal aging.
The differences were greatest in the front and temporal lobes, but there were also significant differences in the parietal and occipital lobes.
There was not a significant difference in the cerebellar volumes.
The cortex was thinner in the left medial orbitofrontal cortex for the patients with depression.
The authors conclude:
“Our data demonstrate conclusively that widespread GM volume abnormalities are present in patients with depression. These alterations are substantial, corresponding to the amount of GM volume loss that, when averaged over the whole brain, would be expected from nearly 14 years of normal aging. The GM loss is also highly regionally specific, with focal regions showing decreases in GM volumes of nearly twice the magnitude of the global measure. The distributed and regionally specific nature of these alterations provides compelling support for considering MDD as a condition that involves the impairment of networks across the brain.”
This study found that patients who had had their first episode of depression had less gray matter volume in the frontal lobe than healthy controls. The lower volume was not correlated with length or severity of the illness. The patients had not yet taken any medication for their depression. The authors suggest that the changes in gray matter could have occurred before the symptoms of depression. (Although they also could have been caused by the depression, we really can’t tell.)
This study found that the gray matter in people with depression is connected differently from in controls.
“Depressed participants had significantly decreased clustering in their brain networks across a range of network densities. Compared with control subjects, depressed participants had fewer hubs primarily in medial frontal and medial temporal areas, had higher degree in the left supramarginal gyrus and right gyrus rectus, and had higher betweenness in the right amygdala and left medial orbitofrontal gyrus.”
and they conclude:
“Networks of depressed individuals are characterized by a less efficient organization involving decreased regional connectivity compared with control subjects. Regional connections in the amygdala and medial prefrontal cortex may play a role in maintaining or adapting to depressive pathology.”