Medical assessment of patients with mental symptoms seeks to identify 2 things:

Physical disorders mimicking mental disorders

Physical disorders accompanying mental disorders

Numerous physical disorders cause symptoms mimicking specific mental disorders (see Table 3: Approach to the Patient With Mental Symptoms: Selected Mental Symptoms Due to Physical Disorders). Other physical disorders may not mimic specific mental syndromes but instead change mood and energy.
Table 2

Selected Mental Symptoms Due to Physical Disorders

Mental Symptom
Physical Disorder*

Confusion, delirium, disorientation
Cerebral arteritis, including that caused by SLE

CNS infection (eg, encephalitis, meningitis, toxoplasmosis)

Complex partial seizures

Dehydration

Drug overdose, including prescription drug overdose

Electrolyte abnormalities

Fever

Hypoglycemia

Hypothermia

Hypothyroidism

Hypoxia

Liver failure

Mass lesion (eg, tumor, hematoma)

Renal failure

Sepsis

Thyroid disorders

Vascular infarct

Vitamin deficiency

Cognitive impairment, behavioral instability
Alzheimer’s and other dementias

HIV/AIDS

Lyme disease

Mass lesion

Multiple sclerosis

Neurosyphilis

Parkinson’s disease

Subdural hematoma

SLE

Thyroid disorders

Vascular infarct

Vitamin deficiency

Delusions
Multiple sclerosis

Polysubstance abuse

Seizure disorders

Depression
Brain tumor

Cancer treatments, including interferon

Cushing’s syndrome

Dementia

Diabetes mellitus

Hypothyroidism

Multiple sclerosis

Sarcoidosis

Euphoria, mania
Brain tumor

Multiple sclerosis

Polysubstance abuse

Hallucinations
Encephalitis

Mass lesion

Migraine

Seizure disorders

Insomnia
Circadian rhythm disorders

Dyspnea or hypoxia

Gastroesophageal reflux disease (GERD)

Hyperthyroidism

Periodic leg movement disorder or restless legs syndrome

Pain syndromes

Irritability
Multiple sclerosis

Vitamin B12 deficiency

Memory impairment
Hypothyroidism

Multiple sclerosis

SLE

Vitamin deficiency

Mood symptoms
HIV/AIDS

Multiple sclerosis

Personality change
Mass lesion

Multiple sclerosis

Seizure disorders

SLE

Psychosis (eg, hallucinations)
Brain tumor

Dementia

Electrolyte abnormalities

Migraine

Multiple sclerosis

Polysubstance abuse

Sarcoidosis

Sensory loss

SLE

Syphilis
*In addition, numerous drugs and toxins may cause mental symptoms.

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

CNS-active drugs (eg, anticonvulsants, antidepressants, antipsychotics, sedative/hypnotics, stimulants)

Anticholinergics (eg, antihistamines)

Corticosteroids

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, amphetamines, cocaine, hallucinogens, and phencyclidine

(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.

In addition to the problem of causing mental symptoms, patients with a mental disorder may develop a physical disorder (eg, meningitis, diabetic ketoacidosis) 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.

Patients presenting for psychiatric care occasionally have undiagnosed physical disorders (including substance abuse, diabetes, and hypothyroidism) that are not the cause of their mental symptoms but nonetheless require evaluation and treatment.
Table 3

Selected Mental Symptoms Due to Physical Disorders

Mental Symptom
Physical Disorder*

Confusion, delirium, disorientation
Cerebral arteritis, including that caused by SLE

CNS infection (eg, encephalitis, meningitis, toxoplasmosis)

Complex partial seizures

Dehydration

Drug overdose, including prescription drug overdose

Electrolyte abnormalities

Fever

Hypoglycemia

Hypothermia

Hypothyroidism

Hypoxia

Liver failure

Mass lesion (eg, tumor, hematoma)

Renal failure

Sepsis

Thyroid disorders

Vascular infarct

Vitamin deficiency

Cognitive impairment, behavioral instability
Alzheimer’s and other dementias

HIV/AIDS

Lyme disease

Mass lesion

Multiple sclerosis

Neurosyphilis

Parkinson’s disease

Subdural hematoma

SLE

Thyroid disorders

Vascular infarct

Vitamin deficiency

Delusions
Multiple sclerosis

Polysubstance abuse

Seizure disorders

Depression
Brain tumor

Cancer treatments, including interferon

Cushing’s syndrome

Dementia

Diabetes mellitus

Hypothyroidism

Multiple sclerosis

Sarcoidosis

Euphoria, mania
Brain tumor

Multiple sclerosis

Polysubstance abuse

Hallucinations
Encephalitis

Mass lesion

Migraine

Seizure disorders

Insomnia
Circadian rhythm disorders

Dyspnea or hypoxia

Gastroesophageal reflux disease (GERD)

Hyperthyroidism

Periodic leg movement disorder or restless legs syndrome

Pain syndromes

Irritability
Multiple sclerosis

Vitamin B12 deficiency

Memory impairment
Hypothyroidism

Multiple sclerosis

SLE

Vitamin deficiency

Mood symptoms
HIV/AIDS

Multiple sclerosis

Personality change
Mass lesion

Multiple sclerosis

Seizure disorders

SLE

Psychosis (eg, hallucinations)
Brain tumor

Dementia

Electrolyte abnormalities

Migraine

Multiple sclerosis

Polysubstance abuse

Sarcoidosis

Sensory loss

SLE

Syphilis
*In addition, numerous drugs and toxins may cause mental symptoms.