Dependence syndrome is a combination of physiological, behavioral, and cognitive phenomena where the use of a psychoactive substance, or a behavioral pattern, takes a central place in the individual's value system. It is a brain disease similar to other chronic illnesses and is characterized by a complex of behavioral disorders resulting from the interaction of genetic, biological, psychosocial factors, and environmental influences.

Dependence syndrome (DS) can be 'chemical' in relation to a specific substance (such as nicotine, alcohol, coffee, salt, sugar), an entire class of substances (such as opioid drugs, stimulants, tranquilizers), or a wide range of pharmacologically different psychoactive substances (according to the ICD-10 definition). It can also be 'non-chemical' and related to behaviors such as gambling, social media use, shopping, video games, overeating/fasting, and so on.