What Is the Genetic Connection Between Anorexia Nervosa and OCD?

What you need to know

• Anorexia nervosa (AN) and obsessive-compulsive disorder (OCD) have significant genetic overlap, with a genetic correlation of 0.49.
• The study found shared genetic risk factors between AN/OCD and other psychiatric disorders like schizophrenia and bipolar disorder.
• Brain areas like the basal ganglia and specific cell types like medium spiny neurons may play a role in the shared genetic risk for AN and OCD.
• AN shows stronger genetic links to metabolic traits compared to OCD, suggesting it may have both psychiatric and metabolic components.

Genetic overlap between anorexia nervosa and OCD

This study aimed to examine the shared genetic architecture between anorexia nervosa (AN) and obsessive-compulsive disorder (OCD). Previous research has found high rates of comorbidity between these disorders, with about 20-50% of AN patients having a lifetime history of OCD, and 5-10% of OCD patients having a history of AN. Family studies have also shown increased risk of OCD in relatives of AN patients.

The researchers conducted a cross-disorder genome-wide association study (GWAS) meta-analysis, combining data from 3,495 AN cases, 2,688 OCD cases, and 18,013 controls. While no individual genetic variants reached genome-wide significance, they found a substantial genetic correlation of 0.49 between AN and OCD. This confirms previous findings of shared genetic risk between the two disorders.

Shared risk with other psychiatric disorders

The study found that the shared AN-OCD genetic risk was positively correlated with other psychiatric disorders, including:

• Bipolar disorder
• Schizophrenia
• Neuroticism

This aligns with previous research showing overlap in genetic risk factors across multiple psychiatric conditions. It suggests there may be some common biological pathways or mechanisms underlying various mental health disorders.

Metabolic and anthropometric associations

Interestingly, the researchers found that AN showed much stronger genetic correlations with metabolic and anthropometric traits compared to OCD. Some key findings include:

• Negative genetic correlations between AN and body mass index, obesity, insulin levels, and triglycerides
• Positive genetic correlation between AN and “good” HDL cholesterol

This suggests that AN may have both psychiatric and metabolic components to its genetic architecture. The metabolic associations appear to be more specific to AN rather than shared with OCD.

Brain regions and cell types implicated

To understand what parts of the brain may be involved in AN-OCD shared risk, the researchers looked at gene expression patterns across different tissues and cell types. They found enrichment of AN-OCD risk genes in:

• The basal ganglia region of the brain
• Medium spiny neurons

The basal ganglia are involved in motor control, executive functions, behaviors, and emotions. Medium spiny neurons are the main type of neuron found in the basal ganglia. These findings align with neuroimaging studies that have implicated the basal ganglia in both AN and OCD.

Conclusions

• There is substantial genetic overlap between anorexia nervosa and OCD, supporting observed clinical connections between the disorders.
• The shared genetic risk also overlaps with other psychiatric conditions, suggesting some common biological pathways.
• Anorexia nervosa shows unique genetic links to metabolic traits that are not shared with OCD.
• Brain circuits involving the basal ganglia may play a role in the shared risk for AN and OCD.