New Genetic Analysis of Psychiatric Disorders Reveals Interconnections

The most comprehensive genetic study on psychiatric disorders to date indicates that many genetic variants are related to several mental health issues, not just one.

This research categorizes 14 psychiatric disorders into five primary groups based on their associated genetic variants. For example, anorexia nervosa, obsessive-compulsive disorder (OCD), and Tourette’s syndrome share a similar genetic profile, linking them together.

The findings, which appeared in a recent issue of Nature, propose that disorders in the same category may arise from common biological mechanisms. Understanding these shared pathways could lead to more effective treatments for a range of mental health issues, according to the research team.

Chunyu Liu, a psychiatry professor at SUNY Upstate Medical University who wasn’t part of the study, mentioned that the results align well with prior studies. He noted, “The shared genetics between schizophrenia and bipolar disorder pointed us in this direction.” While he agrees that genetics indicate shared biological mechanisms, Liu also highlighted that the study doesn’t account for the significant variability in clinical symptoms between these disorders, even if their genetic foundations overlap.

Genomics Beyond Genetics

The research revealed that various genetic variants related to psychiatric disorders are also tied to other traits, including intelligence, sleep issues like insomnia, personality, social behaviors such as aggression, and even socioeconomic status.

Abdel Abdellaoui, a geneticist from the University of Amsterdam who was not involved in the study, explained in a commentary that not every genetic link is negative. For instance, the genetic correlation between schizophrenia and bipolar disorder can also relate to positive traits that facilitate academic success, like creativity and perseverance.

This aspect is particularly significant since embryos used in in vitro fertilization (IVF) may be screened for psychiatric risk indicators based on genetics. Parents can choose embryos with lower “risk scores” for mental health disorders. However, Abdellaoui cautioned that this decision isn’t always straightforward. Just having certain genetic traits doesn’t guarantee the development of a disorder, as those same genes might also foster positive traits like creativity or resilience.

Abdellaoui emphasized that psychiatric conditions often manifest at the extremes of a natural genetic variation spectrum, particularly when coupled with specific life experiences. Essentially, someone might have a genetic tendency for a particular disorder but only develop it in the face of adverse circumstances, such as trauma or environmental stressors. This perspective redefines mental illness as an unfortunate intersection of natural variation and external pressures.

Identifying the Five Groups

To pinpoint which genetic variants are unique to specific disorders and which ones are shared, Andrew Grotzinger, an assistant professor at the Institute for Behavior Genetics, and his colleagues examined genetic data from over a million individuals, mainly of European descent.

Disorders sharing numerous genetic variants were labeled as “genetically correlated.” With these correlations, the researchers categorized the 14 disorders into five genomic factors:

• Compulsive: Anorexia, OCD, Tourette’s
• Neurodevelopmental: Autism, ADHD
• Internalizing: Depression, PTSD, anxiety
• Substance use: Alcohol, cannabis, nicotine, and opioid dependence
• Schizophrenia-bipolar

Each genomic factor displayed a distinct biological pattern regarding gene behavior in the brain. For instance, genes associated with the schizophrenia-bipolar factor are notably active in excitatory neurons, which promote activation in other neurons and in brain regions that help interpret reality.

In contrast, genes belonging to the internalizing factor are related to glial cells, the brain’s supportive cells responsible for immune protection and maintaining neuron connections. This suggests that these disorders may be more associated with support cells than with neurons themselves, Abdellaoui noted.

The substance-use factor involved gene variants that encode enzymes for breaking down alcohol, along with those for nicotine receptors.

Liu urged caution in interpreting these genetic links to psychiatric conditions. “Genes or biological pathways statistically associated with a disorder should not be seen as causal without further evidence of a direct mechanistic role,” he stated. Correlation does not imply causation, he emphasized. There may be various other explanations for the association of certain genes with disorders or for overlapping genetic signals between two disorders.

This article is for informational purposes only and is not meant to offer medical advice.