People with a substance use disorder have distorted thinking, behavior and body functions. Changes in the brain’s wiring are what cause people to have intense cravings for the drug and make it hard to stop using the drug. Brain imaging studies show changes in the areas of the brain that relate to judgment, decision making, learning, memory and behavior control.
These substances can cause harmful changes in how the brain functions. These changes can last long after the immediate effects of the drug — the intoxication. Intoxication is the intense pleasure, calm, increased senses or a high caused by the drug. Intoxication symptoms are different for each substance.
Over time people with addiction build up a tolerance, meaning they need larger amounts to feel the effects.
People with addictive disorders may be aware of their problem, but be unable to stop it even if they want to. The addiction may cause health problems as well as problems at work and with family members and friends. The misuse of drugs and alcohol is the leading cause of preventable illnesses and premature death.
Symptoms of substance use disorder are grouped into four categories:
• Impaired control: a craving or strong urge to use the substance; desire or failed attempts to cut down or control substance use
• Social problems: substance use causes failure to complete major tasks at work, school or home; social, work or leisure activities are given up or cut back because of substance use
• Risky use: substance is used in risky settings; continued use despite known problems
• Drug effects: tolerance (need for larger amounts to get the same effect); withdrawal symptoms (different for each substance)
Many people experience both mental illness and addiction. The mental illness may be present before the addiction. Or the addiction may trigger or make a mental disorder worse.