Psychiatric disorders affect around 10% of the world's population. In addition to diagnosis-specific symptoms, mental disorders such as depression (MDD), bipolar disorder (BD), and schizophrenia (SZ) are associated with linguistic abnormalities, which can also manifest as formal thought disorders (FTD). Structural changes in the superior temporal gyrus are associated with FTD and are thought to be caused by impaired glutamatergic and dopaminergic transmitter systems. Mutations in the transcription factor FOXP2 (forkhead-box P2) can lead to altered structures in brain regions of speech and language. This study investigated the relationships between two SNPs (rs7799109, rs1456031) of FOXP2 and the cognitive function, as well as between the two SNPs and gray matter volumes in healthy controls (HC) and patients with psychiatric disorders (MDD, BD, SZ, schizoaffective disorder (SZA)). Differences were found in verbal episodic memory (BD, rs7799109), lexical word fluency (BD, rs1456031), and verbal working memory (MDD, BD, all patients, rs1456031). In terms of brain morphology, volume differences were found in the left medial precentral gyrus (HC, rs7799109), thalamus/basal ganglia (all patients, rs7799109), and left temporal lobe (SZ and SZA, rs1456031). FOXP2 may play a role in the development of FTD by influencing glutamatergic or dopaminergic transmitter systems and through this effect in brain morphology. Further research is required to identify other potential mechanisms for the development of FTD and to devise preventive, diagnostic and therapeutic options for patients and individuals at risk.
