Bipolar disorder, also known as manic-depressive illness, is a brain disorder that causes unusual shifts in mood, energy, activity levels, and the ability to carry out day-to-day tasks. Symptoms of bipolar disorder are severe. They are different from the normal ups and downs that everyone goes through from time to time. Bipolar disorder symptoms can result in damaged relationships, poor job or school performance, and even suicide. But bipolar disorder can be treated, and people with this illness can lead full and productive lives. In 1800s and early 1900s, individuals dependent on opioids were primarily developed and from middle socioeconomic groups. However, since the 2000s, minorities and lower socioeconomic groups have been recognised with chemical dependence. It shows availability of opioids and subcultural factors in opioid use. Therefore, medical professionals are at higher risk for developing opioid-related disorders. It is estimated that 90% of those with opioid dependence have one or more other mental disorders. Depression is commonly identified. Opioid-dependents report suicidal tendency and insomnia. Other substance use disorders anxiety disorders, antisocial personality disorder, post-traumatic stress disorders are common. Studies shown that disorders like attention-deficit hyperactivity disorder and anti-social personality disorder have genetic variations, and since patients who abuse cocaine have a high incidence of diagnoses, they also genetically deposited to abuse cocaine.

Individuals with mental illness and addiction comprise at least half of the patients in most mental health treatment systems. This combination results in increased risk for frequent psychiatric relapses, poor medication compliance, violence, suicide, legal problems, and high utilization of the emergency room or inpatient services. Traditional mental health and addiction treatments have not adequately addressed these co-occurring disorders due to clinical interventions, programs, and system flaws that have not addressed the individual's needs. Integrated treatment requires both an understanding of mental illness and addiction and the means to integrate and modify the traditional treatment approaches in both the mental health and addiction treatment fields. There is strong evidence to support the efficacy and effectiveness of integrated treatment in this population. All mental health clinicians should become experienced and skilled in the core psychotherapy approaches to treating substance use disorders, including motivational enhancement therapy, relapse prevention, and 12-step facilitation. In addition, integrated treatment includes integrating medications for both addiction and mental illness with the behavioral therapies and other psychosocial interventions.

Dual diagnosis is the condition of suffering from a mental disorder and a co-occurring substance abuse problem. Any patient can have a "dual diagnosis" and treated primarily for an addiction disorder can have a “co-occurring mental disorder”. Like depression and alcoholism. Diagnosing a primary psychiatric illness in substance abusers is challenging as drug abuse itself often induces psychiatric problems, thus making it necessary to differentiate between drug induced and pre-existing mental illness. Drug abuse, including alcohol and prescription drugs, can induce symptoms which resembles mental illness, it is tough to differ substance induced psychiatric syndromes and pre-existing mental health problems. Psychiatric disorders among drug or alcohol abusers disappear with prolonged abstinence.

Addictive disorder is a psychiatric chronic disease of brain reward system, motivation, and memory. Leads to inability to control behaviour, leads to habitual changes, and which affects a person from recovery of substance. Reason for Addictive disorder is substance abuse or activity that gives us pleasure and a genetic variance that increases our interest. Addiction is genetically developed in our psychological system, social and environmental factors that lead to excessive and prolonged usage, tolerance and withdrawal and negative consequences. Foetal alcohol spectrum disorders are a group of diseases that occur in a person whose mother drank alcohol in pregnancy.

Mental health is a level of psychological well-being, or an absence of a mental disorder. It is the "psychological state of someone who is functioning at a satisfactory level of emotional and behavioral adjustment". From the perspective of positive psychology or holism, mental health may include an individual's ability to enjoy life, and create a balance between life activities and efforts to achieve psychological resilience. According to World Health Organization (WHO) mental health includes "subjective well-being, perceived self-efficacy, autonomy, competence, intergenerational dependence, and self-actualization of one's intellectual and emotional potential, among others." WHO further states that the well-being of an individual is encompassed in the realization of their abilities, coping with normal stresses of life, productive work and contribution to their community.

Alcohol and other drugs of abuse have significant impacts on the neuroimmune system. Studies have demonstrated that drugs of abuse interact with the neuroimmune system and alter neuroimmune gene expression and signalling, which in turn contribute to various aspects of addiction. As the key component of the CNS immune system, neuroimmune factors mediate neuroinflammation and modulate a wide range of brain function including neuronal activity, endocrine function, and CNS development. These neuromodulator properties of immune factors, together with their essential role in neuroinflammation, provide a new framework to understand neuroimmune mechanisms mediating brain functional and behavioural changes contributing to addiction. 

Drugs legalization is helpful for medical use of illicit drugs. Drugs commonly considered capable of recreational use include ethanol, cannabis, nicotine, caffeine, and substances within the scope of the United Nations' Single Convention on Narcotic Drugs and Psychotropic Substances. In 2012 it was estimated that about 3% to 6% of people use non-legal drugs. Domestic and International law enforcement agencies are occupied with interdiction efforts against illegal drug use, production, and circulation. Recreational drug use is use of a drug with the primary intention to alter the state of consciousness in order to create positive emotions. The popular concept of this phenomenon puts it closer to a social behaviour that many places around the world tolerate rather than to serious medical conditions.

Drugs legalization is helpful for medical use of illicit drugs. Drugs commonly considered capable of recreational use include ethanol, cannabis, nicotine, caffeine, and substances within the scope of the United Nations' Single Convention on Narcotic Drugs and Psychotropic Substances. In 2012 it was estimated that about 3% to 6% of people use non-legal drugs. Domestic and International law enforcement agencies are occupied with interdiction efforts against illegal drug use, production, and circulation. Recreational drug use is use of a drug with the primary intention to alter the state of consciousness in order to create positive emotions.