Impulsive behavior in cases of substance abuse can be explained in three cyclical stages: anticipation of the substance use (craving), intoxication with the substance (binge) and withdrawal. Because of the impenetrability of this cycle, addiction to substances is considered a neurobiological disorder. Habitual substance use causes the impulsive behavior to eventually develop into a compulsive act. Substance abuse is distinguished by the neurological changes that take place within the drug abuser’s body. Physiologically, the individual usually develops a positive association with their drug of choice, highlighting features such as its ability to relieve stress, the escapism it provides, or its mind-altering qualities. When the abuser is instilled with a sense of craving, the sensation is accompanied by a sense of strain or excitement in wake of the suspense. The anticipation can seem overwhelming, and the need for the substance seems crucial. In an impulsive control disorder, a sense of gratification, pleasure, or relief occurs while abusing substances. The body’s normal stress-coping mechanisms must be utilized to handle the presence of the substance in its system. As the abuser develops a higher tolerance of the substance over time, these stress-coping mechanisms essentially are reformed as a reward mechanism, creating the sense of relief for having obtained the drug. Neurons transmitted throughout the body system, particularly dopamine, opioid peptide, and GABA systems stimulated by serotonin receptors and cannabinoids, encourage the effects of the substance. The act of intoxication is typically followed by a sense of guilt, regret, or self-contempt, which sends the individual into the withdrawal phase. Because the brain’s neurons that normally had controlled stress were reoriented as the reward mechanism, the substance abuse has now coached receptors in the neurological system to expect the presence of this substance. This neutralizes the effect of the substance on the body’s system and builds a higher tolerance; when the drug disappears, the feeling of withdrawal takes over. Whereas a feeling of gratification was felt by the individual while craving the substance, the individual is now pushed into a negative motivational state.
As the substance becomes more addictive, the individual must intake higher amounts of the substance to keep up with this growing tolerance. This often results in overindulgence of the substance as the individual continually increases amounts of intake without awareness of the body’s point of tolerance. Because the stress system has been depleted, coping with the aftermath of drug intake becomes more difficult, usually inducing a sense of guilt in the individual and acute abstinence. This increased presence of stress or anxiety during the abstinence contributes to a heightened vulnerability to relapse, perpetuating the addiction cycle by once again reinforcing the craving mechanism.
The impulsive drug-intake behavior, once a positive motivational state, will move into a compulsive state characterized by negative reinforcement as the cycle continues. Individuals with compulsive behavior (instead of pleasure or gratification as in impulsive acts) experience anxiety or stress before they commit the act of compulsion, and then feel relief after performing the repetitive act. The repetitive compulsions develop as a ritualistic strategy to combat the anxiety.
It is possible for impulsive behavior and compulsive behavior to coexist within the same individual. The serotonin transporter gene SERT that has been identified in obsessive-compulsive disorder has also been found in cases of alcohol dependency. Individuals with impulsive behavior disorders exhibit a lack of emotional control and are more susceptible to substance abuse than people without personality disorders.