Mental disorders due to systemic infections refer to psychiatric disturbances caused by extracranial systemic infections resulting from viruses, bacteria, spirochetes, fungi, parasites, or other microorganisms such as Chinese Taxillus Herb parasites. These include conditions like sepsis, syphilis, cold-damage disease, macula and papule cold-damage disease, malignant malaria, schistosomiasis, human immunodeficiency virus (HIV) infection, among others. No direct evidence of intracranial infection is found.

bubble_chart Etiology

It is caused by external viruses, bacteria, spirochetes, fungi, protozoa, and Chinese Taxillus Herb parasites invading the body and triggering diseases.

bubble_chart Pathogenesis

The occurrence of mental disorders is related to the entry and action of the aforementioned pathogens in the body, but other factors are also involved.

The following points are of significant importance:

1. The toxins of viruses and bacteria cause direct damage to brain cells.

2. Increased metabolism due to illness leads to the accumulation of intermediate metabolic products in the brain.

3. Temporary cerebral edema and cerebral hypoxia during acute infections.

4. Infections cause high fever and excessive sweating in the body, leading to physical exhaustion, nutritional deficiencies, weakness, insufficient energy supply, as well as acid-base imbalance and electrolyte disturbances, which affect brain function.

5. Individual differences, such as the elderly, children, or those with a previously weak constitution, are more prone to mental disorders during physical infections.

Among the combined effects of these factors, the nature of the infection (e.g., the affinity of the pathogen for brain cells), severity, speed, quantity of pathogens, duration of action, and the effectiveness of anti-infection measures play a crucial role in the occurrence of mental disorders.

The clinical manifestations of mental disorders caused by infection depend on whether the infection is acute or chronic. Acute infections often lead to acute mental disorders, primarily characterized by consciousness disturbances, while chronic infections frequently result in chronic mental disorders, such as schizophrenia-like states, depressive states, manic-like states, personality changes, and intellectual disabilities.

Mental disorders associated with several common infectious diseases:

(1) Mental disorders caused by epidemic common cold

This is an acute pestilential respiratory disease caused by the influenza virus. Since the influenza virus has a strong affinity for the central nervous system, it often leads to mental disorders. Reports indicate an incidence rate of 25–35%. The main clinical manifestations include prodromal symptoms such as headache, weakness, fatigue, and sleep-wake cycle disturbances. Subsequently, drowsiness, perceptual disturbances, and feelings of unreality may occur. High fever or severe cases can lead to consciousness disturbances, such as confusion or even delirium. As the condition improves, the patient enters the stage of convalescence, during which depressive states and cerebral asthenia syndrome may be observed. A few cases may develop encephalitis symptoms. The disease course is relatively short, and the prognosis is generally good.

(2) Mental disorders caused by pneumonia

Acute pulmonary infections may lead to consciousness disturbances, often manifesting as confusion or sometimes delirium during the peak of the illness. Chronic pulmonary infections, such as pulmonary subcutaneous nodules, primarily present with depressive states accompanied by memory decline, difficulty concentrating, and slowed thinking.

In the common type, during the high fever phase, patients may experience confusion, disorientation, and perceptual disturbances. Malignant malaria, or cerebral malaria, is characterized by highly virulent, neurotropic plasmodia that can cause brain pathologies such as focal necrosis, hemorrhage, and cerebral edema. This is seen in malaria-endemic areas or immunocompromised patients. Psychiatric symptoms include severe headache with nausea, vomiting, dysphoria, and restlessness, followed by consciousness disturbances such as confusion, delirium, or even unconsciousness. Neurological examinations may reveal obvious pathological signs, spasms, or paralysis. Patients appear apathetic. During the stage of convalescence, depressive states or cerebral asthenia syndrome may occur. In severe cases, intellectual disabilities may develop in the late stage [third stage].

(4) Mental disorders caused by epidemic hemorrhagic fever

Epidemic hemorrhagic fever is an acute pestilential disease prevalent in autumn and winter. The pathogen is likely a virus, though its mechanism of disease remains unclear. The main symptoms include fever and bleeding. The clinical course is divided into the fever phase, hypotensive phase, oliguric phase, polyuric phase, and stage of convalescence. A study reported that among 173 hemorrhagic fever patients, 53 (30.6%) exhibited central nervous system symptoms, all of which involved mental disorders. Pathological examinations revealed congestion, vascular dilation, and necrotic foci on the brain surface and parenchyma. Psychiatric symptoms mostly occur during the hypotensive and oliguric phases, primarily manifesting as drowsiness, delirium, or confusion; or excitement and restlessness, lasting 1–2 weeks. Concurrently, obvious neurological symptoms and pathological signs may appear.

The disease is caused by the rabies virus, which enters the body through bites or scratches from infected dogs or other animals. Negri bodies can be found in the brain parenchyma and basal ganglia. Clinically, it is divided into furious and paralytic types. In the initial stage [first stage], patients experience headache, restlessness, low-grade fever, and abnormal sensations such as itching or numbness at the healed wound site. After 2–3 days, the furious type manifests as hydrophobia, aerophobia, and photophobia. Water, wind, or light can trigger reflexive throat spasms. Patients exhibit tension, fear, and dysphoria. The condition gradually worsens, with generalized spasms, neck stiffness, excessive salivation, high fever, and eventual heart failure or respiratory paralysis. Without treatment, sudden death may occur. The paralytic type primarily presents with limb paralysis and unconsciousness leading to death.

(6) Mental disorders caused by Acquired Immune Deficiency Syndrome

Acquired Immune Deficiency Syndrome, also known as acquired immunodeficiency syndrome (AIDS), is caused by the human T-lymphotropic virus type III (HTLV-III) or lymphadenopathy-associated virus (LAV). It is primarily transmitted through sexual contact, but can also spread via blood and from mother to child. If the virus invades the central nervous system, neuropsychiatric symptoms may occur. Approximately 30–40% of AIDS patients develop central neuropathological changes, including neuronal loss, brain atrophy, glial nodules, and small focal demyelination. In the initial stage [first stage], patients are often influenced by psychosocial factors and exhibit anxiety or depressive states. As the disease progresses, patients may develop dementia-like symptoms, such as forgetfulness, sluggishness, difficulty concentrating, reduced problem-solving ability, reading difficulties, apathy, poor initiative, and social withdrawal. Physical symptoms include lethargy, anorexia, and diarrhea, leading to significant weight loss. Some patients may experience epileptic seizures, mutism, and unconsciousness. AIDS has now become a global public health concern, with no highly effective treatment available. Antiviral agents and immune enhancers may be tried. The key lies in promoting scientific knowledge, strictly managing blood products, and maintaining responsible sexual behavior to prioritize prevention.

bubble_chart Diagnosis

The key diagnostic points are to confirm the evidence of infection. Differential diagnosis focuses on distinguishing between non-infectious organic psychosis and associated functional psychosis.

bubble_chart Treatment Measures

Identify the pathogen and implement systematic, proactive anti-infection treatment along with integrated Chinese and Western medicine therapy. Supportive treatments include: 1. Ensuring adequate nutrition and hydration, maintaining electrolyte and acid-base balance; 2. Improving cerebral circulation; 3. Promoting the recovery of brain cell function, such as administering energy complex solutions. Based on clinical symptoms, small doses of antipsychotics, antidepressants, and anxiolytics with mild side effects may be prescribed. For patients with impaired consciousness, supportive therapy is prioritized. If significant agitation is present, promethazine injections or oral treatment may be administered as appropriate. Nursing care is crucial—environmental and psychological support helps alleviate fear and anxiety. Special attention to safety measures is required for patients with impaired consciousness to prevent self-harm, falls, or impulsive accidents. For patients with depressive moods, vigilance against suicide attempts is essential, and preventive measures should be taken.

bubble_chart Prognosis

It depends on the nature of the infection, the severity of the physical illness (grade III), and the effectiveness of the treatment.