Psychosis is a condition where an individual experiences a disconnection from reality, which can involve a range of disrupted thoughts and perceptions. People experiencing psychosis may encounter hallucinations, such as seeing or hearing things that others do not, or delusions, which are strong beliefs not based in reality. This state can also lead to confused thinking and speaking, making it difficult for the person to distinguish what is real from what is not. This article explores how frequently psychosis occurs within the general population.
General Prevalence Rates
Understanding how common psychosis is involves looking at different measures of its occurrence within a population. Lifetime prevalence refers to the percentage of people who will experience psychosis at any point in their lives. Estimates for lifetime prevalence of all psychotic disorders range between 1.5% and 3.5% of the population. This means that for every 100 people, between one and four individuals may experience a psychotic disorder at some point in their lives.
The 12-month prevalence, which measures how many people experience psychosis within a single year, is generally lower. Pooled median estimates for 12-month prevalence are around 4.03 per 1,000 individuals, or about 0.4%. Incidence, which refers to the rate of new cases developing over a specific period, is approximately 26.6 per 100,000 person-years for all psychotic disorders.
It is important to differentiate between a full psychotic disorder and isolated “psychotic experiences” (PEs). While a psychotic disorder involves a sustained pattern of symptoms, psychotic experiences are more common and can occur outside the context of a diagnosed condition. For example, the lifetime prevalence of at least one psychotic experience is reported by 5.8% of respondents, with hallucinatory experiences being more frequent than delusional ones. These isolated experiences, such as hearing voices, can be reported by up to 15% of the general population, though not all indicate a psychotic disorder.
Demographic Variations in Prevalence
The occurrence of psychosis is not uniform across all groups, with certain demographic factors influencing the likelihood of experiencing it. Age plays a significant role, as the highest risk for a first psychotic episode falls within late adolescence and early adulthood, between 16 and 30 years old. The average age for a first experience of psychosis is reported as 24 years. While childhood-onset schizophrenia is rare, occurring in about 1 in 10,000 children, the incidence of psychotic experiences themselves can peak during late adolescence.
Regarding gender, overall prevalence rates for psychotic disorders are similar between men and women. However, there are nuances in the age of onset; men often experience their first psychotic episode earlier, in their late teens to early 20s, while women have an onset in their late 20s to early 30s. Men may have a higher incidence of schizophrenia specifically. Men are also observed to have more severe negative symptoms and higher rates of substance abuse compared to women in early psychosis.
Geographical location also shows a consistent association with psychosis prevalence. Rates of psychotic disorders are higher in urban areas compared to rural ones. Longitudinal studies have shown a significant association, with a relative risk between 2 and 2.5 for psychotic disorders in urban settings. This “urbanicity effect” suggests that living in densely populated areas may contribute to an elevated risk of psychosis.
Contributing Risk Factors
Several factors are associated with an increased likelihood of developing psychosis. Genetic predisposition is a recognized factor; individuals with a close relative who has a psychotic disorder face a higher risk. While genetics contribute, they are not the sole determinant, as having a genetic predisposition does not guarantee the development of psychosis. Studies show that people genetically predisposed to schizophrenia are at a disproportionately higher risk for psychotic experiences if they also have a history of cannabis use.
Environmental factors also play a role in the onset of psychosis. Exposure to early life trauma, such as childhood trauma, is a well-known risk factor, with individuals who have experienced childhood trauma being three times more likely to have psychotic symptoms. Other environmental contributors include chronic stress, social isolation, and experiences of discrimination. Migration status is also linked to an increased risk, particularly for refugees and migrants from certain regions, with some studies showing a two to three times higher risk of psychosis among migrant groups compared to native-born populations.
Substance use, particularly of high-potency cannabis, is linked to an increased risk of psychosis, especially when used during adolescence. Young individuals who consume higher-potency cannabis between the ages of 16 and 18 are twice as likely to experience psychotic symptoms later in young adulthood compared to those using lower-potency varieties. The concentration of THC, the main psychoactive component in cannabis, has significantly increased over the decades, intensifying this risk.
Challenges in Accurate Measurement
Obtaining precise prevalence data for psychosis presents several challenges. One significant barrier is the stigma associated with mental health conditions, particularly psychosis. Many individuals experiencing psychotic symptoms may not seek professional help or disclose their experiences due to fear of judgment or discrimination, leading to an underreporting of cases in surveys and clinical records.
Diagnostic complexity further complicates accurate measurement. Psychosis is a collection of symptoms that can be part of various mental health conditions, including schizophrenia, bipolar disorder, or severe depression. Differentiating between these conditions and applying diagnostic criteria consistently across studies can be difficult, as symptoms exist on a spectrum and their interpretation can vary.
Accessing at-risk and marginalized populations also poses a challenge for comprehensive epidemiological surveys. Groups that may have higher rates of psychosis, such as homeless individuals, incarcerated populations, or certain ethnic minorities, are often difficult to include in large-scale studies. Their underrepresentation can skew overall prevalence data, as these populations may experience unique stressors and barriers to care that influence their mental health outcomes.