Substance use disorder is a cluster of cognitive, behavioral, and physiological symptoms. Drugs that are taken in excess have in common direct activation of the brain reward system, which is involved in the reinforcement of behaviors and the production of memories. They produce such an intenseactivation of the reward system that normal activities may be neglected.
Addiction is a disorder of the brain’s reward system, which arises through transcriptional and epigenetic mechanisms. Increased dopaminergic activity is seen with almost of all addictive drugs.FosBis a gene transcription factor responsible for addiction. This gene expression directly and positively regulates drug self –administration and reward sensitization through positive reinforcement, while drug sensitivity to aversion.
There is a wide range of symptoms for each type of addiction, but here we are focusing on mental disorders related to abuse/addiction. The symptom profile for the substance/medication – inducedmental disorders resemble independent mental disorders. Examples are delusions, hallucinations, psychoses, major depressive episodes, and anxiety syndromes. The substance induced mental disorders are an important part of the differential diagnoses for the independent psychiatric conditions. Most substance induced mental disorders are likely to improve in a matter of days to weeks of abstinence.
As per DSM V uses the term Substance Use Disorder, mild, moderate, and severe to indicate the severity. Drug addictions and gambling addiction are listed in it for now. Symptoms of withdrawal generally are intense cravings for the substance, anxiety, irritability, nausea, hallucinations, headaches, tremors, vomiting, cramps, and sweating.