How Do Dopamine and Serotonin Genes Contribute to Different Psychiatric Disorders?

What you need to know

• Dopamine and serotonin are important brain chemicals (neurotransmitters) that affect mood, behavior, and mental health
• This study examined how genes involved in dopamine and serotonin function contribute to 8 different psychiatric disorders
• Different disorders showed connections to different groups of genes - ADHD and autism connected more to dopamine genes, while depression and bipolar disorder connected more to serotonin genes

Understanding Dopamine and Serotonin

Dopamine and serotonin are two crucial brain chemicals that help regulate many important functions:

Dopamine affects:

• Movement control
• Motivation and reward
• Focus and attention
• Memory and learning

Serotonin influences:

• Mood and emotions
• Sleep patterns
• Appetite
• Social behavior
• Anxiety levels

When these chemical systems don’t work properly, it can contribute to various mental health conditions. Many psychiatric medications work by targeting these systems.

The Genetic Study

The researchers examined two sets of genes for each neurotransmitter:

• A “core” set containing only the most essential genes directly involved in dopamine/serotonin function
• A “wide” set including additional genes that play supporting roles

They looked at genetic data from over 435,000 people, including:

• People with 8 different psychiatric disorders
• Healthy control subjects

The psychiatric conditions studied were:

• ADHD (Attention-Deficit/Hyperactivity Disorder)
• Anorexia Nervosa
• Autism Spectrum Disorder
• Bipolar Disorder
• Major Depression
• Obsessive-Compulsive Disorder (OCD)
• Schizophrenia
• Tourette’s Syndrome

Key Findings

Gene-Level Results

The study found 67 genes from the dopamine and serotonin systems that were linked to at least one psychiatric disorder. Twelve of these genes were connected to two different disorders, particularly bipolar disorder and schizophrenia.

Some notable findings included:

• The DRD2 gene (which makes the D2 dopamine receptor) was linked to both schizophrenia and depression
• The CACNA1C gene (involved in both dopamine and serotonin function) showed the strongest connection when looking across all disorders combined

Disorder-Specific Patterns

Different disorders showed connections to different parts of the dopamine and serotonin systems:

Dopamine gene connections:

• ADHD
• Autism Spectrum Disorder

Serotonin gene connections:

• Bipolar Disorder
• Major Depression

Brain Expression Patterns

The researchers also looked at how these genes are expressed (activated) in different brain regions. They found some interesting patterns:

• The CTNNB1 gene showed altered expression in the amygdala (an emotion-processing region) in ADHD
• The DNM1 gene showed altered expression in the cortex (involved in higher thinking) across multiple disorders including ADHD, autism, depression, and schizophrenia

Conclusions

• Dopamine and serotonin genes contribute differently to various psychiatric disorders - there isn’t a one-size-fits-all pattern
• Some genes are involved in multiple disorders, supporting the idea that different psychiatric conditions may share some underlying biological mechanisms
• This research helps explain why some medications that target dopamine or serotonin can work for multiple disorders
• The findings could help develop more targeted treatments by identifying specific genes and brain circuits involved in each disorder