Merck Manual

Please confirm that you are a health care professional

honeypot link

Medical Assessment of the Patient With Mental Symptoms


Michael B. First

, MD, Columbia University

Reviewed/Revised May 2022 | Modified Dec 2022
Topic Resources

Patients with mental complaints or concerns or disordered behavior present in a variety of clinical settings, including primary care and emergency treatment centers. Complaints or concerns may be new or a continuation of a history of mental problems. Complaints may be related to coping with a physical condition or be the direct effects of a physical condition on the brain. The method of assessment depends on whether the complaints constitute an emergency or are reported in a scheduled visit. In an emergency, a physician may have to focus on more immediate history, symptoms, and behavior to be able to make a management decision. In a scheduled visit, a more thorough assessment is appropriate.

Medical assessment of patients with mental symptoms seeks to identify 3 things:

  • Physical disorders mimicking mental disorders

  • Physical disorders caused by mental disorders or their treatment

  • Physical disorders accompanying mental disorders

Numerous physical disorders cause symptoms that mimic specific mental disorders (see table Selected Mental Symptoms Due to Physical Disorders Selected Mental Symptoms Due to Physical Disorders Selected Mental Symptoms Due to Physical Disorders ). Other physical disorders may not mimic specific mental syndromes but instead have an impact on mood and energy.

Many drugs cause mental symptoms; the most common classes of drug causes are

Numerous other therapeutic drugs and drug classes have also been implicated; they include some classes that may not ordinarily be considered (eg, antibiotics, antihypertensives). Drugs of abuse, particularly alcohol Alcohol Toxicity and Withdrawal Alcohol (ethanol) is a central nervous system depressant. Large amounts consumed rapidly can cause respiratory depression, coma, and death. Large amounts chronically consumed damage the liver... read more , amphetamines Amphetamines Amphetamines are sympathomimetic drugs with central nervous system stimulant and euphoriant properties whose toxic adverse effects include delirium, hypertension, seizures, and hyperthermia... read more , marijuana (cannabis) Marijuana (Cannabis) Marijuana is a euphoriant that can cause sedation or dysphoria in some users. Psychologic dependence can develop with chronic use, but very little physical dependence is clinically apparent... read more , cocaine Cocaine Cocaine is a sympathomimetic drug with central nervous system stimulant and euphoriant properties. High doses can cause panic, schizophrenic-like symptoms, seizures, hyperthermia, hypertension... read more , hallucinogens Hallucinogens Hallucinogens are a diverse group of drugs that can cause unpredictable, idiosyncratic reactions. Intoxication typically causes hallucinations, with altered perception, impaired judgment, ideas... read more , and phencyclidine Ketamine and Phencyclidine (PCP) Ketamine and phencyclidine are N-methyl-D-aspartate receptor antagonists and dissociative anesthetics that can cause intoxication, sometimes with confusion or a catatonic state. Overdose can... read more (PCP), particularly in overdose, are also frequent causes of mental symptoms. Withdrawal from alcohol, barbiturates, or benzodiazepines may cause mental symptoms (eg, anxiety) in addition to symptoms of physical withdrawal.

Patients with a mental disorder may develop an unrelated physical disorder (eg, meningitis Overview of Meningitis Meningitis is inflammation of the meninges and subarachnoid space. It may result from infections, other disorders, or reactions to drugs. Severity and acuity vary. Findings typically include... read more , diabetic ketoacidosis Diabetic Ketoacidosis (DKA) Diabetic ketoacidosis (DKA) is an acute metabolic complication of diabetes characterized by hyperglycemia, hyperketonemia, and metabolic acidosis. Hyperglycemia causes an osmotic diuresis with... read more ) that causes new or worsened mental symptoms. Thus, a clinician should not assume that all mental symptoms in patients with a known mental disorder are due to that disorder. The clinician may need to be proactive in addressing possible physical causes for mental symptoms, especially in patients unable to describe their physical health because they have psychosis or dementia.

Pearls & Pitfalls

  • Do not assume that all mental symptoms in patients with a known mental disorder are due to that disorder.

Patients presenting for psychiatric care occasionally have undiagnosed physical disorders that are not the cause of their mental symptoms but nonetheless require evaluation and treatment. Such disorders may be unrelated (eg, hypertension Hypertension Hypertension is sustained elevation of resting systolic blood pressure (≥ 130 mm Hg), diastolic blood pressure (≥ 80 mm Hg), or both. Hypertension with no known cause (primary; formerly, essential... read more Hypertension , angina Angina Pectoris Angina pectoris is a clinical syndrome of precordial discomfort or pressure due to transient myocardial ischemia without infarction. It is typically precipitated by exertion or psychologic stress... read more ) or caused by the mental disorder (eg, undernutrition Overview of Undernutrition Undernutrition is a form of malnutrition. (Malnutrition also includes overnutrition.) Undernutrition can result from inadequate ingestion of nutrients, malabsorption, impaired metabolism, loss... read more due to lack of motivation to eat resulting from chronic schizophrenia Schizophrenia Schizophrenia is characterized by psychosis (loss of contact with reality), hallucinations (false perceptions), delusions (false beliefs), disorganized speech and behavior, flattened affect... read more ) or its treatment (eg, hypothyroidism Hypothyroidism Hypothyroidism is thyroid hormone deficiency. Symptoms include cold intolerance, fatigue, and weight gain. Signs may include a typical facial appearance, hoarse slow speech, and dry skin. Diagnosis... read more Hypothyroidism due to lithium, hyperlipidemia Dyslipidemia Dyslipidemia is elevation of plasma cholesterol, triglycerides (TGs), or both, or a low high-density lipoprotein cholesterol (HDL-C) level that contributes to the development of atherosclerosis... read more Dyslipidemia secondary to atypical antipsychotics).



  • New-onset mental symptoms (ie, no prior history of similar symptoms)

  • Qualitatively different or unexpected symptoms (ie, in a patient with a known or stable mental disorder)

  • Mental symptoms that begin at an unexpected age (eg, new-onset psychosis in an older person)

The goal of medical assessment is to diagnose underlying and concomitant physical disorders rather than to make a specific psychiatric diagnosis.


History of present illness should note the nature of symptoms and their onset, particularly whether onset was sudden or gradual and whether symptoms followed any possible precipitants (eg, trauma, illness, starting or stopping of a drug or substance). The clinician should ask whether patients have had previous episodes of similar symptoms, whether a mental disorder has been diagnosed and treated, and, if so, whether patients have stopped taking their drugs.

Review of systems seeks symptoms that suggest possible causes:

Past medical history should identify known physical disorders that can cause mental symptoms (eg, thyroid, liver, or kidney disease; diabetes; HIV or COVID-19 infection). All prescription and over-the-counter drugs should be reviewed, and patients should be queried about any alcohol or illicit substance use (amount and duration). Family history of physical disorders, particularly of thyroid disease and multiple sclerosis, is assessed. Risk factors for infection (eg, unprotected sex, needle sharing, recent hospitalization, residence in a group facility) are noted.

Physical examination

Vital signs are reviewed, particularly for fever, tachypnea, hypertension, and tachycardia. Mental status Examination of Mental Status Examination of Mental Status is assessed, particularly for signs of confusion or inattention.

A full physical examination is done, although the focus is on

Interpretation of findings

The findings from the history and physical examination help interpret possible causes and guide testing and treatment.

Confusion and inattention (reduced clarity of awareness of the environment, suggesting delirium Delirium Delirium is an acute, transient, usually reversible, fluctuating disturbance in attention, cognition, and consciousness level. Causes include almost any disorder or drug. Diagnosis is clinical... read more ), especially if of sudden onset, fluctuating, or both, indicate the presence of a physical disorder. However, the converse is not true (ie, a clear sensorium does not confirm that the cause is a psychiatric disorder). Other findings that suggest a physical cause include

  • Abnormal vital signs (eg, fever, tachycardia, tachypnea)

  • Meningeal signs and symptoms (eg, headache, photophobia, neck rigidity)

  • Abnormalities noted during the neurologic examination, including aphasia

  • Disturbance of gait, balance, or both

  • Incontinence

Some findings help suggest a specific cause, especially when symptoms and signs are new or have changed from a long-standing baseline:

  • Dilated pupils (particularly if accompanied by flushed, hot, dry skin): Anticholinergic drug effects

  • Constricted pupils: Opioid drug effects or pontine hemorrhage

  • Rotary or vertical nystagmus: Phencyclidine intoxication

  • Horizontal nystagmus: Often accompanies diphenylhydantoin toxicity

  • Garbled speech or inability to produce speech: A brain lesion (eg, stroke)

  • A preceding history of relapsing-remitting neurologic symptoms, particularly when a variety of nerves appear to be involved: Multiple sclerosis or vasculitis

  • Stocking-glove paresthesias: Possibly thiamin or vitamin B12 deficiency

In patients with hallucinations, the type of hallucination is not particularly diagnostic except that command hallucinations or voices commenting on the patient’s behavior probably represent a mental disorder.

Symptoms that began shortly after significant trauma or after beginning a new drug may be due to those events. Drug or alcohol use may or may not be the cause of mental symptoms; about 10 to 45% of patients with a mental disorder (varies by diagnosis) also have a substance use disorder Substance Use Disorders Substance use disorders involve a pathologic pattern of behaviors in which patients continue to use a substance despite experiencing significant problems related to its use. Diagnosis of substance... read more (dual diagnosis).

Pearls & Pitfalls

  • A substance use disorder may not be the cause of new mental symptoms; about 10 to 45% of patients with a mental disorder also have a substance use disorder.

Interpretation of findings reference

  • 1. Toftdahl NG, Nordentoft M, Hjorthøj C: Prevalence of substance use disorders in psychiatric patients: A nationwide Danish population-based study. Social psychiatry and psychiatric epidemiology. Soc Psychiatry Psychiatr Epidemiol 51(1):129-140, 2016. doi: 10.1007/s00127-015-1104-4.


Testing varies depending on signs and symptoms. If patients with a known mental disorder have an exacerbation of their typical symptoms and they have no medical complaints, a normal sensorium, and a normal physical examination (including vital signs, pulse oximetry, and fingerstick glucose testing), they do not typically require further laboratory testing other than perhaps measurement of therapeutic drug levels.

Although new onset mental symptoms or marked change in the nature of symptoms in patients with a known mental disorder may be due to a medical rather than mental disorder, it is unclear how commonly such a disorder is asymptomatic and there is no consensus on routine laboratory testing of medically asymptomatic patients. Some clinicians do one or more of the following to screen for potential disorders:

Electrolyte and renal function tests may be diagnostic and help inform subsequent drug management (eg, for drugs that require adjustment in patients with renal insufficiency).

Patients with signs or symptoms of a medical disorder should have testing appropriate to diagnose that disorder:

Less often, findings may suggest testing for systemic lupus erythematosus, syphilis, demyelinating disorders, Lyme disease, or vitamin B12 or thiamin deficiency, especially in patients presenting with signs of dementia.

Toxicology screening (eg, urine drug screen, blood alcohol level) is done if the patient has a recent history of substance use disorder or physical signs suggesting intoxication or recent drug use (eg, needle marks).

Evaluation reference

  • 1. Anderson EL, Nordstrom K, Wilson MP, et al: American Association for Emergency Psychiatry Task Force on Medical Clearance of Adults: Part I: Introduction, review and evidence-based guidelines. West J Emerg Med 18 (2):235–242, 2017. doi: 10.5811/westjem.2016.10.32258.

Drugs Mentioned In This Article

Drug Name Select Trade
Eskalith, Eskalith CR, Lithobid
Aluvea , BP-50% Urea , BP-K50, Carmol, CEM-Urea, Cerovel, DermacinRx Urea, Epimide-50, Gord Urea, Gordons Urea, Hydro 35 , Hydro 40, Kerafoam, Kerafoam 42, Keralac, Keralac Nailstik, Keratol, Keratol Plus, Kerol, Kerol AD, Kerol ZX, Latrix, Mectalyte, Nutraplus, RE Urea 40, RE Urea 50 , Rea Lo, Remeven, RE-U40, RYNODERM , U40, U-Kera, Ultra Mide 25, Ultralytic-2, Umecta, Umecta Nail Film, URALISS, Uramaxin , Uramaxin GT, Urea, Ureacin-10, Ureacin-20, Urealac , Ureaphil, Uredeb, URE-K , Uremez-40, Ure-Na, Uresol, Utopic, Vanamide, Xurea, X-VIATE
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
quiz link

Test your knowledge

Take a Quiz!