**1. Introduction**

The *adolescent* and *younger adult* periods defined by the World Health Organization (WHO) as the transition from childhood to adulthood play a vital role in the lives of

individuals. These periods are mental and physical developmental processes in which tendency to substance abuse, nutritional disorders, mental problems, and risky behaviors are common. Gorker et al. [1] stated in their study that patients who referred to the child and adolescent psychiatry clinic were diagnosed with anxiety disorder, mood disorder, mental retardation, expulsion disorder, disruptive behavior disorder, borderline intellectual functioning, communication disorder, somatoform disorder, and tic disorders, respectively. It is stated in the aforesaid study that these diagnoses are accompanied by mental retardation, adjustment disorder, attention deficit, and hyperactivity, as well as substance use disorder (SUD). There are studies demonstrating that substances with addiction potential are preferred by adolescents and young people due to their euphoric effect, which is generally seen as a positive effect and to relieve negative effects such as pain, pain-reducing, stressrelieving, and relaxing [2]. However, chronic use of a limited number of classes of substances that begin with such justifications causes physical, psychological, and behavioral changes in humans. Substance Use Disorder (SUD) appears under the influence of multiple factors and the persistence is accompanied by these factors. Environmental factors including family, peer relations, neighborhood relations, and physical conditions of neighborhood and educational environment play various roles in addiction-related situations such as molecular pathways, cellular mechanisms, tolerance in addiction, recurrence of addiction, and substance seeking.

The family is closely involved with individual's developmental behavior disorders, with respect to its cultural roots and family attitudes. Biological effects can be classified under many factors, such as genetical, physiological, temperamental, and impulsive behavior tendencies. Nonetheless, family is the first social unit that the individual belongs to. The baby is born in a family and learns the first social rules from the family. Due to this reason, it's said that family has an impact on individuals both in biological and sociological personality development. Biological disposition—namely temperament—is transferred by genetical heritage while sociological disposition namely character—is related with upbringing attitudes, attachment, cultural heritage. Studies have brought out that in SUD, having a substance user family member plays a crucial role in individual's life [3].

The SUD refers to tolerance and withdrawal that occurs after chronic use of the substance, which is a tool that an individual uses to cope with many factors that he calls negative effects especially between 11 and 16 years of age or to feel himself belonging to a group; however, behavioral addiction refers to uncontrollable, permanent use despite negative physical, psychological, social, or legal consequences. Bozkurt [4] shared the findings in their study that child-raising attitudes of the parents are effective. Among substance addicted individuals, 20.9% of the participants stated that they were exposed to physical violence and 40.9% stated that there was physical violence in the family. Furthermore, it was determined that 69.8% of the participants had a substance use disorder in their families. Ünal [5] stated in his study that participants had family members with SUD including fathers by 25%, siblings by 50%. The family is also the society in which the temperament structure of the individual, namely genetic tendencies, is also effective. An individual is born with genetic predispositions in the family. There are studies showing that individuals with COMT, DRD2, PER3, eNOS, NR3C1 functional gene variants are prone to develop MID.

The gene variant is a term used to describe the variation in the DNA sequence in the genome. The term variant may be used to describe a change that may be benign, pathogenic, or with an unknown significance.

*The Analysis on the Effects of COMT, DRD2, PER3, eNOS, NR3C1 Functional Gene Variants… DOI: http://dx.doi.org/10.5772/intechopen.106313*

DNA methylation is the reaction of covalent attachment of a methyl group from the 5-carbon of cytosine in a CpG dinucleotide to the structure, altering gene expression and altering the cell functions.

The aim of this study was to analyze the effects of COMT, DRD2, PER3, eNOS, NR3C1 functional gene variants and COMT, DRD2, and NR3C1 methylation status on the tendencies that have the potential detected in individuals with MID through decision trees algorithm. The criminal record history, continuum of substance use, former polysubstance abuse, attempted suicide, and inpatient treatment will be analyzed by using decision trees.
