Genetics and epigenetics play critical roles in mental health, offering insights into the complex interplay between biological predisposition and environmental influences in the development and progression of mental disorders. Genetic studies have identified numerous risk loci associated with conditions such as schizophrenia, bipolar disorder, and depression, highlighting the polygenic nature of these illnesses. However, the presence of genetic risk factors alone does not fully account for the variability in disease onset, severity, or response to treatment. This gap is increasingly understood through the lens of epigenetics, which involves heritable changes in gene expression that do not alter the DNA sequence itself but are influenced by environmental factors, such as stress, diet, and exposure to toxins. Epigenetic mechanisms, including DNA methylation, histone modification, and non-coding RNAs, can modulate gene activity in response to external stimuli, leading to long-lasting effects on brain function and behavior. These processes are particularly important during critical periods of brain development, where epigenetic modifications can shape neural circuits involved in emotion regulation, cognition, and stress response. Emerging research suggests that the interaction between genetic predisposition and epigenetic changes contributes to the heterogeneity observed in mental health disorders, explaining why individuals with similar genetic risks can have different outcomes. Understanding these intricate genetic and epigenetic networks is essential for developing personalized therapeutic strategies, which could revolutionize the prevention, diagnosis, and treatment of mental health conditions. Advances in this field hold the promise of identifying biomarkers for early intervention and creating targeted interventions that consider an individual’s unique genetic and epigenetic profile, ultimately improving mental health outcomes on a global scale.