الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 180 |  |  |
| | | from | 180 | | |
Abstract
Attention deficit hyperactivity disorder (ADHD) is the most prevalent neurodevelopmental disorder in childhood that causes great social, academic, and health problems (Cagigal et al., 2019). It is characterized by difficulties in two domains: inattention and hyperactivityimpulsivity with three primary subtypes; predominantly inattentive, hyperactive-impulsive and combined presentations. Symptoms usually persist over time, extend in several settings and lead to significant impairment (Asherson et al., 2016). Substance use disorders (SUDs) can be defined as a group of chronic relapsing disorders, characterized by compulsion to seek and take drugs, loss of control in limiting intake, and emergence of a negative emotional state (e.g., dysphoria, anxiety, irritability) when access to the drug is denied. from a diagnostic perspective, the term addiction is now encompassed by the term substance use disorders. In 2013, DSM- 5 combined what was previously conceptualized as two separate and hierarchical disorders (substance abuse and substance dependence) into one construct, defining substance use disorders on a range from mild to moderate to severe, with the severity of an addiction depending on how many of the established criteria apply (Koob and Volkow, 2016). ADHD has a high comorbidity with substance use disorders (SUD). The high co-heritability of ADHD and SUD is seen in twin and adoption studies suggests that there are common genes sharing in etiology of both problems. Other studies suggest that there may be numerous genetic insults that increase vulnerability to ADHD and SUD. No single gene has been shown to make more than a small contribution (Ocana, 2010). Psychiatric disorders were observed in up to 85% of adolescents with SUD. ADHD is one of the most common overlapping disorders in early-onset SUD. Longitudinal data suggested that childhood ADHD could persist into adolescence in 75% of cases and into adulthood in approximately one-half of cases (Kessler et al., 2006 and Wilens et al., 2012). The overlap between ADHD and SUD in adolescents and adults is one of the areas of increasing clinical and public health interest. The understanding of the increased risk of SUD within ADHD may give more targeted treatments for both disorders at earlier stages of their expression with the results of reduced morbidity, disability and better long-term prognosis in adolescents and adults.