Schizophrenia is one of the most serious disorders affecting human health today, with complex and diverse signs and symptoms, usually divided into positive, negative, cognitive, affective, and motor symptoms. Currently, schizophrenia is not a preventable disorder; however, implementing effective prevention measures for people in the ultra-high risk (UHR) stage in an effort to reduce risk factors may help reduce its incidence. Early assessment and intervention are difficult but important. This article reviews the research advances in early prevention and intervention for schizophrenia.
Early prevention
Primary prevention targets all healthy individuals and aims to reduce the number of new cases;
Secondary prevention and early intervention should be used to identify and treat patients at the early signs of the disease, i.e., the pre-onset and prodromal stages, with the aim of impeding disease progression;
Tertiary prevention refers to measures to prevent the incapacitation of individuals affected by the disease and to reduce relapse, social and legal problems caused by the disease and the associated suicide rate. Early prevention and intervention in schizophrenia has positive implications.
Universal prevention
Although it is not clear which risk factors should be included in the context of universal prevention of schizophrenia, reports suggest that certain risk factors can increase the likelihood of developing schizophrenia and are generally recognized.
These risk factors include: biological indicators, susceptibility genes, or neuropsychological abnormalities.
A study conducted in Norway and Denmark confirmed that educating the general public about recognizing signs and symptoms of psychosis through schools, general practitioners, and mass media can reduce the duration of untreated psychosis (DUP) (i.e., the time it takes from onset to treatment).
Other examples of universal prevention include instructing women of childbearing age on prenatal care and reducing prenatal and postnatal risk factors; and improving public health measures and reducing the use of prohibited drugs. Recently, the role of diet has received increasing attention, for example, the role of polyunsaturated fatty acids and vitamin D in preventing the progression of schizophrenia has attracted attention.
Selective prevention
Also known as targeted prevention, this is the targeting of risk factors for the development of schizophrenia.
These risk factors (environmental and genetic) are obtained on a case-by-case screening basis. Several environmental factors have been reported to be associated with an increased risk of developing schizophrenia, including prenatal infection or malnutrition, perinatal complications, winter birth, lack of effective protection in the home environment, experience of physical and sexual abuse as a child, urbanization of the living environment, marijuana use, unemployment, marital status, and migration.
The correlation between genetic factors and gene-environment interactions and the onset of schizophrenia may be 80%. Studies have shown that having a family member with schizophrenia leads to a significant increase in the prevalence of the disorder in the family, as Keshavan et al. reported an increased prevalence of psychotic behavior abnormalities in late childhood and adolescence in the offspring of parents with schizophrenia compared to children of normal parents. However, there is insufficient evidence to support a definitive association between genetic variants and the onset of schizophrenia, so its diagnostic significance is unclear.
Directed prevention
The key issue in directional prevention is the early recognition of characteristic signs and symptoms of mental illness. Early symptoms of schizophrenia include mild positive symptoms, negative symptoms, cognitive impairment, and motor impairment, which some scholars refer to as the “ultra-high risk stage (UHR). Because many high-risk individuals do not ultimately develop schizophrenia, the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) introduced the concept of “mild psychotic syndrome (APS)” to describe this concept.
However, the DMS-5 concluded that the available data were insufficient to establish sufficiently reliable criteria for the assessment of APS to be clinically applicable. Therefore, further research is needed to clarify the concept of APS.
As mentioned above, UHR has no specific symptoms and is therefore difficult to identify a priori, and knowledge of this stage has been gained mainly through retrospective studies of patients with schizophrenia. Studies have shown that the use of UHR can identify populations vulnerable to schizophrenia. More than one-third of the population of UHR subjects not receiving antipsychotic medication develop a critical state of schizophrenia within 1 year; at 10 years of follow-up, the proportion developing schizophrenia approaches 70%.
It has also been shown that individuals in the UHR population with predominantly negative symptoms and cognitive impairment have a higher probability of developing schizophrenia, characteristics that are beneficial for early identification of UHR.
Retrospective studies have found that of the three prevention interventions, the most cost-effective is directed prevention. This approach is more effective and more ethical, with fewer overall adverse effects. Therefore, the majority of clinical prevention interventions are focused on individuals with prodromal symptoms. For individuals with schizophrenia and related prodromal symptoms, interventions may be attenuated and delayed as appropriate.
Early intervention has been applied in three areas: targeted prevention for individuals with precursors or prodromal symptoms of psychosis, treatment measures to improve prognosis for individuals with confirmed psychosis, and identification of individuals with untreated illness.
Research Advances in Early Intervention
Early intervention can help reduce the morbidity and disability associated with schizophrenia. However, due to the lack of effective early identification methods, the diagnosis of schizophrenia is usually established only after the patient presents with specific psychotic symptoms. This invariably prolongs the DUP, and a longer DUP represents a relatively poorer treatment outcome. On the other hand depression and suicide risk are increased, which may increase substance abuse and delinquency and raise the cost of treatment.
Several early intervention studies for UHR have been reported successively. The Personal Assessment and Crisis Evaluation Service (PACE), conducted by the Early Psychosis Prevention Intervention Centre (EPPIC) established at the University of Melbourne, Australia, is the world’s first study based on early assessment, treatment intervention for schizophrenia. The study conducted PACE assessments for UHR populations, i.e., assessments and interventions for people at high risk for psychosis. The first tool for assessing UHR, the Comprehensive Assessment of At-Risk Mental Status (CAARMS), was developed.