Attention-deficit/hyperactivity disorder (ADHD) is the most frequently diagnosed neurobehavioral disorder in children and young adults (Schilling, Walsh & Yun, 2011). Though there is a breadth of research on the topic, the fact that individuals with ADHD have to overcome many difficulties throughout their life, like failing to inhibit inappropriate actions that can otherwise lead to antisocial behavior, severe injuries and in many cases end with imprisonment with 40-70% of detainees being diagnosed with ADHD (Rösler et al. 2004, as cited by Schilling, Walsh & Yun, 2011), suggests that there is still necessity to discuss the dominant explanations for this disability. The following essay is going to briefly state the definition of ADHD according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), it will then outline and evaluate the present genetic and evolutionary position on ADHD.
The DSM-5 describes ADHD as a disorder that is characterized by constant inattention and/or hyperactivity-impulsivity appearing in numerous situations more regularly and severely than is usual for individuals in the same developmental stage. There are three main types of ADHD; the first type is the predominantly inattentive type. Individuals being diagnosed with this form of ADHD show difficulty to follow conversations or instructions and are easily distracted. The second type of ADHD is the predominantly hyperactive-impulsive type, which manifests in restlessness and impulsivity. The third type of ADHD is a combination of both (Schilling, Walsh & Yun, 2011). For the sake of succinctness the author is not going to discuss each subtype separately, but rather provide a general account on the combined type of ADHD.
The precise causation of ADHD is unknown, and the fact that it is a multidimensional disability that often manifests in subgroups or comorbid with other disabilities like conduct disorder (CD) and oppositional defiant disorder (ODD) (Comings, 2005, as cited by Schilling, Walsh & Yun, 2011) makes a general characterization difficult. With that being said, a large number of family, twin and adoption studies have shown an ADHD heritability of .80 suggesting a high heritability (Killeen, Tannock & Sagvolden, 2012).
However, the researchers Killeen, Tannock and Sagvolden (2012) suggested that even though many studies show a genetic component in the development of ADHD, there have been no adoption studies with monozygotic twins reared apart. Thus, findings that support the heritability hypothesis, provided by family studies, can be misinterpreted, as situational factors like familial difficulties, unemployment, single parent families, low SES, low education, poor neighborhoods, harsh disciplinary techniques, conflictual marital relationships, and maternal smoking can also be causal factors for ADHD (Killeen, Tannock & Sagvolden, 2012). Thus, there are many different possibilities why a child develops ADHD and these triggers are not necessarily...