Objectives:
The present study analyzed the polymorphism of the dopamine receptor gene DRD4, which is widely described in the literature as being associated with sensation seeking. Gambling disorder (GD) shares similar biological mechanisms and symptoms with substance use disorders (SUD). Therefore, a behavioral addiction group was selected for this study. During the research and recruitment process, it was revealed that all individuals undergoing treatment for gambling addiction were also addicted to amphetamine, which aligns with the biological mechanism related to brain neurotransmission

Methods:
The study sample consisted of 307 male participants: 107 men diagnosed with both gambling and amphetamine addiction (study group), and 200 non-addicted men without psychiatric disorders, who served as the control group. Both groups underwent psychometric assessment using the State-Trait Anxiety Inventory (STAI) and the NEO Five-Factor Personality Inventory, and were evaluated by a board-certified psychiatrist. Genomic DNA was extracted from peripheral blood according to standard protocols. The DRD4 Ex3 polymorphism was genotyped using the PCR technique

Results:
Among individuals with gambling and amphetamine addiction who showed higher scores on the trait scale of the STAI and higher levels of Neuroticism, the s/s polymorphism of the DRD4 Ex3 gene occurred significantly more frequently compared to the control group with s/s, l/l, and s/l polymorphisms. Similarly, in addicted individuals with higher trait STAI scores and higher Neuroticism levels, the s/l polymorphism of the DRD4 Ex3 gene was significantly more prevalent than in the control group with s/s polymorphism. These findings indicate that the s/s and s/l genotypes occurred significantly more frequently in men addicted to gambling and amphetamine than in the control group, which may suggest an association between these DRD4 Ex3 variants and susceptibility to addiction

Conclusions:
The present study demonstrates that addictions should be analyzed through a multifactorial lens. A correlation was observed between the DRD4 polymorphism and personality traits associated with addiction