There isn’t one single drug that “makes you go crazy,” but several substances are well known for triggering psychotic symptoms like paranoia, hallucinations, delusions, and violent or erratic behavior. Methamphetamine, PCP, cocaine, synthetic cathinones (bath salts), and high doses of cannabis are among the most common culprits. Even some prescription medications, including corticosteroids, can push people into temporary psychosis. The risk depends on the drug, the dose, how long someone has been using it, and their individual brain chemistry.
Methamphetamine
Methamphetamine is one of the drugs most strongly linked to psychotic behavior. Roughly 40% of regular meth users experience psychotic symptoms at some point, and studies of people with meth dependence put the rate between 26% and 46%. These symptoms include intense paranoia, seeing or hearing things that aren’t there, and believing others are plotting against you. Some users describe feeling convinced that people are watching them through walls or that insects are crawling under their skin.
Meth floods the brain with dopamine, the chemical involved in reward and motivation. At normal levels, dopamine helps you focus and feel pleasure. At the levels meth produces, it overwhelms the brain’s ability to regulate its own signaling. Specifically, the excess dopamine and a related chemical called glutamate damage a type of brain cell responsible for keeping other neurons in check. When those “braking” cells stop working properly, brain activity becomes chaotic and disorganized. The result looks a lot like schizophrenia, and researchers actually use meth-induced psychosis as a model to study that illness.
PCP (Phencyclidine)
PCP, sometimes called angel dust, has a long reputation for causing extreme and unpredictable behavior. It works by blocking a receptor in the brain involved in learning, memory, and perception. This produces a dissociative state where users feel detached from their body and surroundings, often with severe confusion. Unlike most other drugs on this list, PCP is specifically associated with unprovoked aggression, self-mutilation, and a dramatically increased pain threshold, meaning people under its influence may not stop even when injured.
Behavioral responses vary widely from person to person. Reported effects include delirium, hallucinations, disorientation, muscle rigidity, irregular speech, agitation, and convulsions. Both temporary and chronic psychosis have been documented. The combination of impaired judgment, dissociation from pain, and potential for violent outbursts is what gives PCP its particular notoriety. Ketamine, a related drug, works on the same receptor system and can produce similar dissociative and hallucinatory effects, though typically with less aggression.
Cocaine
Cocaine powerfully blocks the reabsorption of dopamine, leaving abnormally high levels active in the brain. Among people with moderate to severe cocaine dependence, psychotic symptoms occur in up to 80% of users. The most common presentation is paranoia: a deep, consuming suspicion that others are threatening you. Hallucinations, particularly hearing voices or sounds, also occur. These symptoms tend to intensify with repeated use over short periods, sometimes called binge patterns, and can escalate rapidly.
Synthetic Cathinones (Bath Salts)
Synthetic cathinones, sold under the street name “bath salts,” gained widespread attention in the early 2010s for producing extreme agitation and bizarre behavior. The U.S. Drug Enforcement Administration lists their psychiatric effects as confusion, acute psychosis, combativeness, aggression, violent and self-destructive behavior, paranoia, hallucinations, and delusions. These drugs are stimulants that act on the same dopamine system as meth and cocaine, but their chemical composition varies widely from batch to batch, making reactions unpredictable. Users may not know exactly what they’ve taken or how potent it is.
Cannabis in High Doses
Cannabis is less commonly associated with dramatic behavioral outbursts, but it does cause psychotic symptoms more often than many people realize. Among people with severe cannabis dependence, up to 80% report experiencing paranoia or hallucinations while using. Cannabis affects the brain partly through its influence on dopamine regulation, which may explain why heavy use can trigger symptoms that overlap with stimulant-induced psychosis. The risk roughly doubles for developing a psychotic illness among cannabis users compared to non-users, and this association is strongest in people who already carry genetic risk factors for schizophrenia.
Anticholinergic Drugs and Deliriants
A lesser-known category involves drugs that block a brain chemical called acetylcholine. Scopolamine, found in certain motion sickness patches and also in plants like jimsonweed, can produce a particularly disturbing form of psychosis. Unlike stimulant psychosis, where people are typically aware something is wrong afterward, anticholinergic delirium involves full hallucinations that feel completely real, profound confusion, agitation, rambling speech, and paranoid delusions. One of the most striking effects is total amnesia: people have no memory of what they did or experienced while under the influence.
Physical symptoms accompany the mental effects. These include a racing heart, dangerously elevated body temperature, dry skin, dilated pupils, and involuntary muscle jerking. The loss of both self-control and memory is what makes scopolamine particularly dangerous, and why it has been used criminally in some countries to incapacitate victims.
Prescription Medications
Some prescription drugs cause psychiatric disturbances that surprise both patients and their families. Corticosteroids, commonly prescribed for inflammation, allergies, and autoimmune conditions, cause mild to moderate psychiatric reactions in about 28% of patients and severe reactions in nearly 6%. Short-term use tends to produce euphoria or hypomania (an elevated, impulsive state), while long-term use leans more toward depression. Full psychosis, including delusions and hallucinations, is possible. These reactions typically appear early in the treatment cycle and usually resolve when the dose is lowered or stopped, though some cases require additional medication to manage.
Previous psychiatric history doesn’t reliably predict who will react this way. Someone who tolerated corticosteroids fine once may have a severe reaction the next time, and vice versa.
Why Some People Are More Vulnerable
Not everyone who takes these substances experiences psychosis, which raises the question of why some people “go crazy” on a drug while others don’t. Genetics play a significant role. People who carry a higher burden of gene variants associated with schizophrenia are more likely to use cannabis and to use it in greater quantities, and they’re more likely to develop psychotic symptoms when they do. Schizophrenia itself is up to 80% heritable, meaning the genetic foundation for psychotic vulnerability is often already present before any drug enters the picture.
Other risk factors include the amount used, how long someone has been using, sleep deprivation (especially common with stimulant binges), and whether multiple substances are combined. A person using meth for three days without sleep is at far greater risk than someone who tried it once.
How Long Drug-Induced Psychosis Lasts
For most people, the psychosis stops when the drug clears the body. In a study of patients hospitalized for drug-induced psychotic symptoms, 60% recovered within one month of stopping the substance. Another 30% took one to six months. The remaining 10% still had psychotic symptoms after six months, and this group was significantly more likely to be rehospitalized later and to have ongoing psychotic symptoms at follow-up. That 10% may represent people whose drug use triggered or unmasked a longer-lasting psychotic illness like schizophrenia.
Clinically, substance-induced psychotic disorder is diagnosed when hallucinations or delusions develop during or within a month of intoxication or withdrawal, and when the symptoms don’t persist far beyond the drug’s influence. If psychotic symptoms continue long after the substance is gone, or if they existed before the drug use started, a separate psychotic disorder is the more likely explanation.