Substance Use Disorder are defined as problematic patterns of substance use causing clinically significant impairment or distress leading to dependency or addiction. Addiction is taken as a chronic brain disorder involving long-lasting changes in brain networks responsible for reward, executive function, stress reactivity, mood, and self-awareness. These changes drive the intense urge to consume substances and the loss of control over this urge. In addition to its detrimental impacts on an individual's health, it also affects their well-being, and functioning, and is influenced by factors such as curiosity, peer group culture, mental health issues like anxiety and depression, recreation, and the examples set by parents regarding substance use.

According to WHO, 400 million people lived with alcohol use disorders globally; 209 million with alcohol dependence. In addition to that, an estimated 331 million people used other drugs in 2024, equivalent to 6.2 per cent of the world’s population aged 15 to 64. Cannabis remained the most widely used drug, with 256 million users, followed by opioids (63 million), amphetamines (32 million), cocaine (25 million) and ecstasy (21 million). This has resulted in 3.6 million annual deaths from alcohol and drug use. In the UK, there is a 6% rise this year in adults in contact with drug and alcohol treatment services.

These statistics merely represent the tip of the iceberg, as a significant portion of substance use disorders remains hidden as many cases go uncounted, meaning these statistics are lower than reality. Also, tobacco is not accounted for in the statistics, due to its legal status of use in most parts of the world.