A variant of the gene that encodes the neurotransmitter metabolizing enzyme monoamine oxidase-A (MAOA), which relates to neural systems involved in aggression, plays a key role in regulating behavior following threatening events. Brain imaging studies show patterns of arousal in areas of the brain that are associated with aggression in response to emotion-provoking stimuli. Prenatal factors and birth complications
Many pregnancy and birth problems are related to the development of conduct problems. Malnutrition, specifically protein deficiency, lead poisoning or exposure to lead, and mothers use of alcohol or other substances during pregnancy may increase the risk of developing ODD. In numerous research, substance use prior to birth has also been associated with developing disruptive behaviors such as ODD. Although pregnancy and birth factors are correlated with ODD, strong evidence of direct biological causation is lacking. Neurobiological factors
Deficits and injuries to certain areas of the brain can lead to serious behavioral problems in children. Brain imaging studies have suggested that children with ODD may have hypofunction in the part of the brain responsible for reasoning, judgment, and impulse control. Children with ODD are thought to have an overactive behavioral activation system (BAS), and an underactive behavioral inhibition system (BIS). The BAS stimulates behavior in response to signals of reward or non-punishment. The BIS produces anxiety and inhibits ongoing behavior in the presence of novel events, innate fear stimuli, and signals of non-reward or punishment. Neuroimaging studies have also identified structural and functional brain abnormalities in several brain regions in youths with conduct disorders.
Research looking precisely at the etiological factors linked with ODD is limited. The literature often examines common risk factors linked with all disruptive behaviors, rather than ODD specifically. Symptoms of ODD are also often believed to be the same as CD, even though the disorders have their own respective set of symptoms. When looking at disruptive behaviors such as ODD, research has shown that the causes of behaviors are multi-factorial. However, disruptive behaviors have been identified as being mostly due either to biological or environmental factors. Genetic influences
Research indicates that parents pass on a tendency for externalizing disorders to their children that may be displayed in multiple ways, such as inattention, hyperactivity, or oppositional and conduct problems. Research has also shown that there is a genetic overlap between ODD and other externalizing disorders. Heritability can vary by age, age of onset, and other factors. Adoption and twin studies indicate that 50% or more of the variance causing antisocial behavior is attributable to heredity for both males and females. ODD also tends to occur in families with a history of ADHD, substance use disorders, or mood disorders, suggesting that a vulnerability to develop ODD may be inherited. A difficult temperament, impulsivity, and a tendency to seek rewards can also increase the risk of developing ODD. New studies into gene variants have also identified possible gene-environment (G x E) interactions, specifically in the development of conduct problems.