Teens with anhedonia — a symptom of depression marked by an inability to experience pleasure — are found to have lower levels of the neurotransmitter GABA in a vital mood-regulating section of the brain, according to a NIMH-funded study published in the Archives of General Psychiatry. Anhedonia is found in up to 59 percent of depressed teens.
In young people, symptoms of depression can be highly varied and often overlap with symptoms of other disorders. This tends to make adolescent depression more difficult to study when using conventional research tools and methods. However, by focusing on specific symptoms and using various kinds of measuring systems, researchers may be able to discover the pathways and processes underlying depression and other mental disorders.
Guided by research on adults, Vilma Gabbay, M.D., of New York University School of Medicine, and a team set out to focus on the neurotransmitter GABA, which plays a vital role throughout the body and is involved in regulating brain cell communication.
Abnormalities in GABA production or function in the brain have been linked to anhedonia and several other mental disorders, including schizophrenia, postpartum depression, and possibly learning disorders.
The researchers used a specialized MRI to measure GABA levels in the anterior cingulate cortex (ACC) in 20 depressed teens, half of whom also had anhedonia. These levels were compared to those of 21 matched controls who did not have depression or anhedonia.
Teens with depression and anhedonia had significantly lower ACC GABA levels than the control subjects. Lower ACC GABA levels were associated with more severe anhedonia symptoms among all volunteers.
The results support that GABA plays a role in anhedonia and depression among teens. Furthermore, by correlating GABA levels with numeric measures of anhedonia severity, the researchers were able to evaluate the individuals’ symptoms along a continuum.
Continuous or “dimensional” measurements—rather than traditional measures that limit symptoms to being classified as either present or absent—may offer stronger specificity to disease evaluations in research.
Further studies in larger populations are needed to confirm these results. Advances in imaging technology may help identify how other neurotransmitters play into depression as well.