Neurotransmitter-Linked SNPs as Candidate Markers for Dual Diagnosis of Mental Health and Substance Use Disorders

This preprint reports a genome-wide association study (GWAS)-based analysis identifying ten candidate single-nucleotide polymorphisms (SNPs) across nine neurotransmitter-related genes as potential markers for dual diagnosis- the co-occurrence of mental health and substance use disorders. The study integrates published brain expression quantitative trait loci (eQTL) data from GTEx v8, PsychENCODE, and the UK Brain Expression Consortium (UKBEC) to characterize functional consequences of panel SNPs, identifies three convergent mechanistic pathways (dopaminergic reward dysregulation, BDNF neuroplasticity, and NEGR1 affective circuit remodelling), and proposes a provisional polygenic risk score (PRS) framework. All data analyses used publicly available, de-identified genomic data. No primary human subjects data were collected. This is a preprint and has not been peer reviewed.