###### Abstract  
Introduction: Psychometric disorders are a mental illness that affect 3% of the world's population. The external (cannabis) and internal vulnerability factors (polymorphisms of the AKT1 gene, the COMT gene and the DAT1 gene) acquire special relevance in the appearance of psychosis; this is known as the vulnerability-stress model. Objective: To analyze the scientific evidence that reflects the relationship between the polymorphism of the AKT1 gene and the consumption of cannabis in the appearance of psychosis. Material and Methods: The bibliographic search was made using databases such as Scopus, WoS, Cochrane Library, TRIP Database, PubPsych and PubMed. The criteria of the \"MeSH\" terminology and the inclusion and exclusion criteria were followed, obtaining a total of 22 articles that comprises this narrative review. Results: The presence of genetic variation in the locus rs2494732 of the AKT1 gene in a cannabis user raises the risk of the appearance of psychosis, especially if homozygous with the C allele. Likewise, consumption entails a slowdown in the functionality of the AKT1 gene, releasing a greater amount of dopamine in the striatum through the involvement of indirect mechanisms. Similarly, the COMT gene and the interaction of the AKT1 gene with the DAT1 gene raise the risk of developing psychotic disorder. Conclusion: The genetic polymorphism rs2494732 of AKT1 is the main factor responsible for the appearance of psychosis, although polymorphisms of the COMT and DAT1 gene are also implicated. Regarding the AKT1 gene, subjects with two copies of the C allele have a higher risk of developing psychosis compared to subjects with two copies of the T allele. It should also be noted that the muscarinic receptors rs115455482 and r\(\alpha\)74722579 are related to a greater vulnerability to psychosis and the development of psychotic disorders. psychosis; psychotic disorder; schizophrenia; severely mental disorder; AKT1; cannabis; THC; cannabinoid; marijuana +
Footnote †: journal: Applied Sciences  
other health problems based on morbidity and mortality statistics in different countries or demographic areas and at different times, and the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), belonging to the American Psychiatric Association (APA), which offers a diagnostic classification of various mental disorders to facilitate diagnosis and treatment for professionals [6]. The APA organizes severe mental illness (SMI) into 18 disorder groups, one of them being the spectrum of schizophrenia and other psychotic disorders [6]. Psychotic disorders comprise several mental illnesses whose characteristics are listed in Table 1[3; 5]:  
Psychosis can be functional and organic; despite the fact that in both there is a loss of contact with reality, they differ in that in the first category there is no objectifiable organic cause, while in the second there is [7]. From the first manifestations that make up the first episode of psychosis (PEP), it is possible to act early [8]. Some factors that confer greater vulnerability favoring its appearance are shown in Table 2:  
As psychosis has a multifactorial etiology, it requires an interaction between various causal factors to precipitate its appearance, which is known as the vulnerability-stress model [8; 9; 10]. This model indicates that there are people who are more vulnerable to acquire certain conditions, due to the presence of internal causal factors such as genetic predisposition or damage to brain structures, which, when interacting with external causal factors such as social changes, responses to stressful situations or drug abuse, cause it to manifest the said condition [9]. Genetic-environmental interaction can occur passively (genetic factors and the person's development environment), evocatively (the person's actions in social situations will evoke the response of others) and actively (behaviors and personal attitudes will interfere in a greater or lesser exposure to external causal factors) [10].