Symptoms can sometimes come and go with wave-like reoccurrences or fluctuations in severity of symptoms. Common symptoms include impaired cognition, irritability, depressed mood, and anxiety; all of which may reach severe levels which can lead to relapse.

The protracted withdrawal syndrome from benzodiazepines can produce symptoms identical to generalized anxiety disorder as well as panic disorder. Due to the sometimes prolonged nature and severity of benzodiazepine withdrawal, abrupt withdrawal is not advised.

Common symptoms of post-acute withdrawal syndrome are:

- Psychosocial dysfunction

- Anhedonia

- Depression

- Impaired interpersonal skills

- Obsessive-compulsive behaviour

- Feelings of guilt

- Autonomic disturbances

- Pessimistic thoughts

- Impaired concentration

- Lack of initiative

- Craving

- Inability to think clearly

- Memory problems

- Emotional overreactions or numbness

- Sleep disturbances

- Physical coordination problems

- Stress sensitivity

- Increased sensitivity to pain

- Panic disorder

- Generalized anxiety disorder

- Sleep disturbance (dreams of using, behaviors associated with the life style)

Symptoms occur intermittently, but are not always present. They are made worse by stress or other triggers and may arise at unexpected times and for no apparent reason. They may last for a short while or longer. Any of the following may trigger a temporary return or worsening of the symptoms of post-acute withdrawal syndrome:

- Stressful and/or frustrating situations

- Multitasking

- Feelings of anxiety, fearfulness or anger

- Social conflicts

- Unrealistic expectations of oneself

Disturbances in mental function can persist for several months or years after withdrawal from benzodiazepines. Psychotic depression persisting for more than a year following benzodiazepine withdrawal has been documented in the medical literature. The patient had no prior psychiatric history. The symptoms reported in the patient included, major depressive disorder with psychotic features, including persistent depressed mood, poor concentration, decreased appetite, insomnia, anhedonia, anergia and psychomotor retardation. The patient also experienced paranoid ideation (believing she was being poisoned and persecuted by co-employees), accompanied by sensory hallucinations. Symptoms developed after abrupt withdrawal of chlordiazepoxide and persisted for 14 months. Various psychiatric medications were trialed which were unsuccessful in alleviating the symptomatology. Symptoms were completely relieved by recommending chlordiazepoxide for irritable bowel syndrome 14 months later. Another case report, reported similar phenomenon in a female patient who abruptly reduced her diazepam dosage from 30 mg to 5 mg per day. She developed electric shock sensations, depersonalisation, anxiety, dizziness, left temporal lobe EEG spiking activity, hallucinations, visual perceptual and sensory distortions which persisted for years.

A clinical trial of patients taking the benzodiazepine alprazolam (Xanax) for as little as 8 weeks triggered protracted symptoms of memory deficits which were still present after up to 8 weeks post cessation of alprazolam.

Common symptoms include:

- Sudden changes in behaviour – may engage in secretive or suspicious behaviour

- Mood changes – anger towards others, paranoia and little care shown about themselves or their future

- Problems with work or school – lack of attendance

- Changes in eating and sleeping habits

- Changes in friendship groups and poor family relationships

- A sudden unexplained change in financial needs – leading to borrowing/stealing money

There are many more symptoms such as physical and psychological changes, though this is often dependent on which drug is being abused. It is, however, common that abusers will experience unpleasant withdrawal symptoms if the drug is taken away from them.

It is also reported that others have strong cravings even after they have not used the drug for a long period of time. This is called being "clean". To determine how the brain triggers these cravings, multiple tests have been done on mice. It is also now thought that these cravings can be explained by substance-related disorders as a subcategory of personality disorders as classified by the DSM-5.

People with discontinuation syndrome have been on an antidepressant for at least four weeks and have recently stopped taking the medication, whether abruptly, after a fast taper, or each time the medication is reduced on a slow taper. Commonly reported symptoms include flu-like symptoms (nausea, vomiting, diarrhea, headaches, sweating) and sleep disturbances (insomnia, nightmares, constant sleepiness). Sensory and movement disturbances have also been reported, including imbalance, tremors, vertigo, dizziness, and electric-shock-like experiences in the brain, often described by sufferers as "brain zaps". Mood disturbances such as dysphoria, anxiety, or agitation are also reported, as are cognitive disturbances such as confusion and hyperarousal.

In cases associated with sudden discontinuation of MAO inhibitors, acute psychosis has been observed. Over fifty symptoms have been reported.

Most cases of discontinuation syndrome last between one and four weeks, are relatively mild, and resolve on their own; in rare cases symptoms can be severe or extended. Paroxetine ("Paxil") and venlafaxine ("Effexor") seem to be particularly difficult to discontinue and prolonged withdrawal syndrome lasting over 18 months have been reported with paroxetine.

A 2009 Advisory Committee to the FDA found that online anecdotal reports of discontinuation syndrome related to duloxetine ("Cymbalta") included severe symptoms and exceeded prevalence of both paroxetine ("Paxil") and venlafaxine ("Effexor") reports by over 250% (although acknowledged this may have been influenced by duloxetine being a much newer drug). It also found that the safety information provided by the manufacturer not only neglected important information about managing discontinuation syndrome, but also explicitly advised against opening capsules, a practice required to gradually taper dosage.

Both alcoholic hallucinosis and DTs have been thought of as different manifestations of the same physiological process in the body during alcohol withdrawal. Alcoholic hallucinosis is a much less serious diagnosis than delirium tremens. Delirium tremens (DTs) do not appear suddenly, unlike alcoholic hallucinosis. DTs also take approximately 48 to 72 hours to appear after the heavy drinking stops. A tremor develops in the hands and can also affect the head and body. A common symptom of delirium tremens is that people become severely uncoordinated. The biggest difference between alcoholic hallucinosis and delirium tremens is that alcoholic hallucinosis have a much better prognosis than DTs. Moreover, delirium tremens can be fatal when untreated.

Substance abuse, also known as drug abuse, is a patterned use of a substance (drug) in which the user consumes the substance in amounts or with methods which are harmful to themselves or others.

The drugs used are often associated with levels of intoxication that alter judgment, perception, attention and physical control, not related with medical or therapeutic effects. It is often thought that the main abused substances are illegal drugs and alcohol; however it is becoming more common that prescription drugs and tobacco are a prevalent problem.

Substance-related disorders, including both substance dependence and substance abuse, can lead to large societal problems. It is found to be greatest in individuals ages 18–25, with a higher likelihood occurring in men compared to women, and urban residents compared to rural residents. On average, general medical facilities hold 20% of patients with substance-related disorders, possibly leading to psychiatric disorders later on. Over 50% of individuals with substance-related disorders will often have a "dual diagnosis," where they are diagnosed with the substance abuse, as well as a psychiatric diagnosis, the most common being major depression, personality disorder, anxiety disorders, and dysthymia.

The most documented symptoms are cravings for nicotine, anger/irritability, anxiety, depression, impatience, trouble sleeping, restlessness, hunger or weight gain, and difficulty concentrating. Symptoms are usually strongest for the first few days and then dissipate over 2-4 weeks. Withdrawal symptoms make it harder to quit nicotine products and most methods for quitting smoking involve reducing nicotine withdrawal. The most common symptoms are irritability, anxiety and difficulty concentrating. Depression and insomnia are the least common. Other withdrawal symptoms may include constipation, cough, dizziness, drowsiness, headache, impulsivity, fatigue, flu symptoms, mood swings, mouth ulcers, and increased dreaming. Cessation of nicotine usually increases eating and weight, decreases memory, decreases the ability to pay attention and concentrate on tasks, and decreases heart rate. Cessation of tobacco can also require changes in levels of various medications.

The symptoms of stimulant psychosis vary depending on the drug ingested, but generally involve the symptoms of organic psychosis such as hallucinations, delusions, paranoia, and thought disorder.

The cause of alcoholic hallucinosis is unclear. It seems to be highly related to the presence of dopamine in the limbic system with the possibility of other systems. There are many symptoms that could possibly occur before the hallucinations begin. Symptoms include headache, dizziness, irritability, insomnia, and indisposition. Typically, alcoholic hallucinosis has a sudden onset.

The main symptoms of delirium tremens are nightmares, agitation, global confusion, disorientation, visual and auditory hallucinations, tactile hallucinations, fever, high blood pressure, heavy sweating, and other signs of autonomic hyperactivity (fast heart rate and high blood pressure). These symptoms may appear suddenly, but typically develop two to three days after the stopping of heavy drinking, being worst on the fourth or fifth day. Also, these "symptoms are characteristically worse at night". In general, DT is considered the most severe manifestation of alcohol withdrawal and occurs 3–10 days following the last drink. Other common symptoms include intense perceptual disturbance such as visions of insects, snakes, or rats. These may be hallucinations, or illusions related to the environment, e.g., patterns on the wallpaper or in the peripheral vision that the patient falsely perceives as a resemblance to the morphology of an insect, and are also associated with tactile hallucinations such as sensations of something crawling on the subject—a phenomenon known as formication. Delirium tremens usually includes extremely intense feelings of "impending doom". Severe anxiety and feelings of imminent death are common DT symptoms.

DT can sometimes be associated with severe, uncontrollable tremors of the extremities and secondary symptoms such as anxiety, panic attacks and paranoia. Confusion is often noticeable to onlookers as those with DT will have trouble forming simple sentences or making basic logical calculations.

DT should be distinguished from alcoholic hallucinosis, the latter of which occurs in approximately 20% of hospitalized alcoholics and does not carry a significant mortality. In contrast, DT occurs in 5–10% of alcoholics and carries up to 15% mortality with treatment and up to 35% mortality without treatment. DT is characterized by the presence of altered sensorium; that is, a complete hallucination without any recognition of the real world. DT has extreme autonomic hyperactivity (high pulse, blood pressure, and rate of breathing), and 35-60% of patients have a fever. Some patients experience seizures.

Though less common than stimulant psychosis, stimulants such as cocaine and amphetamines as well as the dissociative drug phencyclidine (PCP, angel dust) may also cause a theorized severe and life-threatening condition known as excited delirium. This condition manifests as a combination of delirium, psychomotor agitation, anxiety, delusions, hallucinations, speech disturbances, disorientation, violent and bizarre behavior, insensitivity to pain, elevated body temperature, and superhuman strength. Despite some superficial similarities in presentation excited delirium is a distinct (and more serious) condition than stimulant psychosis. The existence of excited delirium is currently debated.

Supersensitivity psychosis is used to discuss the spontaneous occurrence of psychotic episodes and/or the appearance of tardive dykinesia in the wake of anti-psychotic medication withdrawal.

Such spontaneous episodes have occurred even in patients who never had psychotic episodes before beginning the medication. Studies using Clozapine have found significant evidence.

Larger discussions of withdrawal from other antipsychotics usually focus on tardive dyskinesia, a far more significant and long-lasting side effect of antipsychotic treatment.

When supersensitivity psychosis was explored in 1978, a featured concern was increasing resistance to medication, requiring higher doses or not responding to higher doses. Some articles use the term tardive psychosis to reference to this specific concept. However, articles have disputed its' validity. The condition has been discovered in very few people. Palmstierna asserts that tardive psychosis is a combination of "several different and not necessarily correlated phenomena related to neuroleptic treatment of schizophrenia."

However, some articles use the term tardive psychosis as equivalent to supersensitivity psychosis.

Comedown or crashing is the deterioration in mood that happens as a psychoactive drug, typically a stimulant, is either decreasing or is cleared from the blood and thus the cerebral circulation. The improvement and deterioration of mood (euphoria and dysphoria) are represented in the cognitive as high and low elevations; thus, after the drug has "elevated" the mood (a state known as a high), there follows a period of "coming back down," which often has a distinct character from withdrawal in stimulants. Generally, a comedown ("down", "low", sometimes "crash") can happen to anyone as a transient symptom, but in people who are dependent on the drug (especially those addicted to it), it is an early symptom of withdrawal and thus can be followed by others. Various drug classes, most especially stimulants and to a lesser degree opioids and sedatives, are subject to comedowns. A milder analogous mood cycle can happen even with blood sugar levels (thus sugar highs and sugar lows), which is especially relevant to people with diabetes mellitus and to parents and teachers managing children's behavior, as well as in adults with ADHD. Stimulant comedowns are unique in that they often appear very abruptly after a period of focus or high, and are typically the more intensely dysphoric phase of withdrawal than that following complete elimination from the bloodstream. Besides general dysphoria, this phase can be marked by frustration, anger, anhedonia, social withdrawal, and other symptoms characteristic to a milder mixed episode in bipolar disorder. Alertness and other general stimulant effects are still present.

Signs and symptoms of opioid overdose include, but are not limited to:

- Pin-point pupils may occur. Patient presenting with dilated pupils may still be suffering an opioid overdose.

- Decreased heart rate

- Decreased body temperature

- Decreased breathing

- Altered level of consciousness. People may be unresponsive or unconscious.

- Pulmonary edema (fluid accumulation in the lungs)

- Shock

- Death

Cannabis withdrawal symptoms can occur in one half of patients in treatment for cannabis use disorders. These symptoms include dysphoria (anxiety, irritability, depression, restlessness), disturbed sleep, gastrointestinal symptoms, and decreased appetite. Most symptoms begin during the first week of abstinence and resolve after a few weeks.

According to the National Cannabis Prevention and Information Centre in Australia, a sign of cannabis dependence is that an individual spends noticeably more time than the average recreational user recovering from the use of or obtaining cannabis. For some, using cannabis becomes a substantial and disruptive part of an individual's life and he or she may exhibit difficulties in meeting personal obligations or participating in important life activities, preferring to use cannabis instead. People who are cannabis dependent have the inability to stop or decrease using cannabis on their own.

Antidepressant discontinuation syndrome is a condition that can occur following the interruption, dose reduction, or discontinuation of antidepressant drugs, including selective serotonin re-uptake inhibitors (SSRIs) or serotonin–norepinephrine reuptake inhibitors (SNRIs). The symptoms can include flu-like symptoms and disturbances in sleep, senses, movement, mood, and thinking. In most cases symptoms are mild, short-lived, and resolve without treatment. More severe cases may be successfully treated by reintroduction of the drug, provided reintroduction is done in a timely fashion. Symptoms, including tardive akathisia, and Post SSRI Sexual Dysfunction (PSSD) may persist for months to years, yet may spontaneously resolve after prolonged presence.

Signs and symptoms of opioid intoxication include:

- Decreased perception of pain

- Euphoria

- Confusion

- Desire to sleep

- Nausea

- Constipation

- Miosis

Typically the severity of the symptoms experienced will depend on the amount and duration of prior alcohol consumption, as well as the number and severity of previous withdrawals. Even the most severe of these symptoms can occur in as little as 2 hours after cessation; therefore, the overall unpredictability necessitates either pre-planned hospitalization, treatment coordinated with a doctor, or at the very least rapid access to medical care, and a supporting system of friends or family should be introduced prior to addressing detoxification. In many cases, however, symptoms follow a reasonably predictable time frame as exampled below:

Six to 12 hours after the ingestion of the last drink, withdrawal symptoms such as shaking, headache, sweating, anxiety, nausea or vomiting occur. Other comparable symptoms may also exist in this period. Twelve to 24 hours after cessation, the condition may progress to such major symptoms as confusion, hallucinations (with awareness of reality), tremor, agitation, and similar ailments.

At 24 to 48 hours following the last ethanol ingestion, the possibility of seizures should be anticipated. Meanwhile, none of the earlier withdrawal symptoms will have abated. Seizures carry the risk of death for the alcoholic.

Although, most often, the patient's condition begins to improve past the 48-hour mark, it can sometimes continue to increase in severity to delirium tremens, characterized by hallucinations that are indistinguishable from reality, severe confusion, more seizures, high blood pressure and fever which can persist anywhere from 4 to 12 days.

Cocaine is a powerful stimulant known to make users feel energetic, happy, talkative, etc. In time, negative side effects include increased body temperature, irregular or rapid heart rate, high blood pressure, increased risk of heart attacks, strokes and even sudden death from cardiac arrest. Many habitual abusers develop a transient, manic-like condition similar to amphetamine psychosis and schizophrenia, whose symptoms include aggression, severe paranoia, restlessness, confusion and tactile hallucinations; which can include the feeling of insects under the skin (formication), also known as "coke bugs", during binges. Users of cocaine have also reported having thoughts of suicide, unusual weight loss, trouble maintaining relationships, and an unhealthy, pale appearance.

Cocaine dependence is a psychological desire to use cocaine regularly. Cocaine overdose may result in cardiovascular and brain damage, such as: constricting blood vessels in the brain, causing strokes and constricting arteries in the heart; causing heart attacks.

The use of cocaine creates euphoria and high amounts of energy. If taken in large, unsafe doses, it is possible to cause mood swings, paranoia, insomnia, psychosis, high blood pressure, a fast heart rate, panic attacks, cognitive impairments and drastic changes in personality.

The symptoms of cocaine withdrawal (also known as "comedown or crash") range from moderate to severe: dysphoria, depression, anxiety, psychological and physical weakness, pain, and compulsive cravings.

Nicotine withdrawal is the effect that nicotine-dependent individuals experience after they discontinue or decrease nicotine use. Nicotine is an addictive substance found most commonly in tobacco and tobacco products including cigarettes, cigars, chewing tobacco, pipe tobacco, snus, snuff, and most e-cigarette liquid. Withdrawal is the body’s reaction to not having the nicotine it had become accustomed to. Withdrawal is most common and intense in cigarette smokers and intermediate in smokeless users. The symptoms of nicotine withdrawal usually appear 2-3 hours after last intake of nicotine and peak in 2-3 days. In a minority of smokers, cravings may last for years. Nicotine withdrawal causes few physical signs and is not life-threatening but associated cravings can be as severe as withdrawal from other drugs. There is some evidence that stopping nicotine may make a prior psychiatric problem worse but this is uncertain. After the initial withdrawal period, anxiety, depression, and quality of life generally improve such that former smokers are better off than continuing smokers.

Signs and symptoms of alcohol withdrawal occur primarily in the central nervous system. The severity of withdrawal can vary from mild symptoms such as sleep disturbances and anxiety to severe and life-threatening symptoms such as delirium, hallucinations, and autonomic instability.

Withdrawal usually begins 6 to 24 hours after the last drink. It can last for up to one week. To be classified as alcohol withdrawal syndrome, patients must exhibit at least two of the following symptoms: increased hand tremor, insomnia, nausea or vomiting, transient hallucinations (auditory, visual or tactile), psychomotor agitation, anxiety, tonic-clonic seizures, and autonomic instability.

The severity of symptoms is dictated by a number of factors, the most important of which are degree of alcohol intake, length of time the individual has been using alcohol, and previous history of alcohol withdrawal. Symptoms are also grouped together and classified:

- Alcohol hallucinosis: patients have transient visual, auditory, or tactile hallucinations, but are otherwise clear.

- Withdrawal seizures: seizures occur within 48 hours of alcohol cessations and occur either as a single generalized tonic-clonic seizure or as a brief episode of multiple seizures.

- Delirium tremens: hyperadrenergic state, disorientation, tremors, diaphoresis, impaired attention/consciousness, and visual and auditory hallucinations. This usually occurs 24 to 72 hours after alcohol cessation. Delirium tremens is the most severe form of withdrawal and occurs in 5 to 20% of patients experiencing detoxification and 1/3 of patients experiencing withdrawal seizures.

The signs and symptoms of benzodiazepine dependence include feeling unable to cope without the drug, unsuccessful

attempts to cut down or stop benzodiazepine use, tolerance to the effects of benzodiazepines, and withdrawal symptoms when not taking the drug. Some withdrawal symptoms that may appear include anxiety, depressed mood, depersonalisation, derealisation, sleep disturbance, hypersensitivity to touch and pain, tremor, shakiness, muscular aches, pains, twitches, and headache. Benzodiazepine dependence and withdrawal have been associated with suicide and self-harming behaviors, especially in young people. The Department of Health substance misuse guidelines recommend monitoring for mood disorder in those dependent on or withdrawing from benzodiazepines.

Benzodiazepine dependence is a frequent complication for those prescribed for or using for longer than four weeks, with physical dependence and withdrawal symptoms being the most common problem, but also occasionally drug-seeking behavior. Withdrawal symptoms include anxiety, perceptual disturbances, distortion of all the senses, dysphoria, and, in rare cases, psychosis and epileptic seizures.

Include the following:

- Depression

- Shaking

- Feeling unreal

- Appetite loss

- Muscle twitching

- Memory loss

- Motor impairment

- Nausea

- Muscle pains

- Dizziness

- Apparent movement of still objects

- Feeling faint

- Noise sensitivity

- Light sensitivity

- Peculiar taste

- Pins and needles

- Touch sensitivity

- Sore eyes

- Hallucinations

- Smell sensitivity

All sedative-hypnotics, e.g. alcohol, barbiturates, benzodiazepines and the nonbenzodiazepine Z-drugs have a similar mechanism of action, working on the GABA receptor complex and are cross tolerant with each other and also have abuse potential. Use of prescription sedative-hypnotics; for example the nonbenzodiazepine Z-drugs often leads to a relapse back into substance misuse with one author stating this occurs in over a quarter of those who have achieved abstinence.

Cannabis use is associated with comorbid mental health problems, such as mood and anxiety disorders, and discontinuing cannabis use is difficult for some users. Psychiatric comorbidities are often present in dependent cannabis users including a range of personality disorders.