Thursday, November 5, 2015

Schizophrenia spectrum disorder

Most people have felt depressed or anxious, even if those feelings have never become debilitating. And how many times have you heard someone say, “I'm a little OCD”? Clearly, people intuitively think that most mental illnesses have a spectrum, ranging from mild to severe. Yet most people do not know what it feels like to hallucinate—to see or hear things that are not really there—or to have delusions, persistent notions that do not match reality. You're psychotic, or you're not, according to conventional wisdom.

Evidence is growing, however, that there may be no clear dividing line. Psychiatrists have long debated whether psychosis exists on a spectrum, and researchers have been investigating the question for more than a decade now. A 2013 meta-analysis, combining much of the existing data, by Jim van Os of Maastricht University in the Netherlands and Richard Linscott of the University of Otago in New Zealand, found the prevalence of hallucinations and delusions in the general population was 7.2 percent—much higher than the 0.4 percent prevalence of schizophrenia diagnoses found in recent studies. Now the most comprehensive epidemiological study of psychotic experiences to date, published in July in JAMA Psychiatry, has given researchers the most detailed picture yet of how many people have these experiences and how frequently. The results strongly imply a spectrum—and suggest that the standard treatment for a psychotic episode might be due for an overhaul.

The researchers, led by John McGrath of the University of Queensland in Australia, analyzed data from the World Health Organization's World Mental Health Surveys, a set of community surveys carried out between 2001 and 2009, involving 31,261 adults in 18 countries. After ruling out experiences caused by drugs or sleep, the researchers determined that 5.8 percent of the respondents had psychotic experiences. Two thirds of these people had had only one type of episode, with hallucinations being four times more common than delusions.

The psychotic experiences were typically rare, with 32 percent of sufferers having only a single episode and another 32 percent having two to five. The other third reported between six and more than 100. Having more than one type of experience was linked to having more in total. These people were not seeking help, and none had been diagnosed with a psychotic disorder. “Most people have only fleeting, sporadic experiences, but there's a subgroup that have a lot, and they're persistent,” McGrath says.

The results suggest psychosis indeed exists on a spectrum, but whether it is distributed in a continuous way across the population remains to be seen. “Is it that we all have a bit of schizophrenia in us, or are there some people who do, and some who don't?” Linscott asks. One complication is that what counts as a hallucination can be a difficult line to draw, and even carefully crafted research surveys can be open to interpretation. “It could be that what we see at the margins are these subtleties due to the language used in the questions,” he says.

The psychotic experiences were slightly more common in women (6.6 percent) than men (5 percent), even though full-fledged schizophrenia is more prevalent in males. In addition, psychotic experiences were more prevalent among people living in middle- and high-income countries (7.2 and 6.8 percent, respectively) than low-income countries (3.2 percent). Being unemployed or unmarried or being from a relatively low-income family was also associated with higher rates of hallucinations and delusions. Socioeconomic and environmental factors such as stress are known risk factors for schizophrenia...

Jenny does not have schizophrenia, but she has hallucinations. “I could feel Mark in the room, standing behind me,” she says of one such experience. “My first love, whom I hadn't seen since I was a teenager, still guiding me, as he had ever since my hallucinations started taking definite shape. I glimpsed him out of the corner of my eye, stroking my spreading wings, reassuring me I'd made the right decision, to leave my old life behind and travel to England to be a journalist.” Jenny, who requested that her real name be withheld for privacy, agreed to talk with me about her hallucinations, which she regards as benign. When she hallucinates, she always sees Mark, and he always offers her advice. He is the part of herself she turns to for guidance.

Jenny believes that her childhood experiences and her mother's mental health issues predisposed her to psychosis—perhaps not surprisingly, because there is a known genetic component. A study last year strongly implicated 108 genetic regions as culprits in schizophrenia. Psychologists have told Jenny that the content of her experiences may be related to a lack of adequate psychological support in childhood, causing her to internalize her own support network. Where mental health is concerned, it seems, nature and nurture are almost always inextricably intertwined.

1 comment:

  1. McGrath JJ, Saha S, Al-Hamzawi A, Alonso J, Bromet EJ, Bruffaerts R,
    Caldas-de-Almeida JM, Chiu WT, de Jonge P, Fayyad J, Florescu S, Gureje O, Haro
    JM, Hu C, Kovess-Masfety V, Lepine JP, Lim CC, Mora ME, Navarro-Mateu F, Ochoa S, Sampson N, Scott K, Viana MC, Kessler RC. Psychotic Experiences in the General Population: A Cross-National Analysis Based on 31,261 Respondents From 18 Countries. JAMA Psychiatry. 2015 Jul;72(7):697-705.



    Community-based surveys find that many otherwise healthy individuals report histories of hallucinations and delusions. To date, most studies have focused on the overall lifetime prevalence of any of these psychotic experiences (PEs), which might mask important features related to the types and frequencies of PEs.


    To explore detailed epidemiologic information about PEs in a large multinational sample.


    We obtained data from the World Health Organization World Mental Health Surveys, a coordinated set of community epidemiologic surveys of the prevalence and correlates of mental disorders in representative household samples from 18 countries throughout the world, from 2001 through 2009. Respondents included 31,261 adults (18 years and older) who were asked about lifetime and 12-month prevalence and frequency of 6 types of PEs (2 hallucinatory experiences and 4 delusional experiences). We analyzed the data from March 2014 through January 2015.


    Prevalence, frequency, and correlates of PEs.


    Mean lifetime prevalence (SE) of ever having a PE was 5.8% (0.2%), with hallucinatory experiences (5.2% [0.2%]) much more common than delusional experiences (1.3% [0.1%]). More than two-thirds (72.0%) of respondents with lifetime PEs reported experiencing only 1 type. Psychotic experiences were typically infrequent, with 32.2% of respondents with lifetime PEs reporting only 1 occurrence and 31.8% reporting only 2 to 5 occurrences. We found a significant relationship between having more than 1 type of PE and having more frequent PE episodes (Cochran-Armitage z = -10.0; P < .001). Lifetime prevalence estimates (SEs) were significantly higher among respondents in middle- and high-income countries than among those in low-income countries (7.2% [0.4%], 6.8% [0.3%], and 3.2% [0.3%], respectively; χ²₂ range, 7.1-58.2; P < .001 for each) and among women than among men (6.6% [0.2%] vs 5.0% [0.3%]; χ²₁ = 16.0; P < .001). We found significant associations with lifetime prevalence of PEs in the multivariate model among nonmarried compared with married respondents (χ²₂ = 23.2; P < .001) and among respondents who were not employed (χ²₄= 10.6; P < .001) and who had low family incomes (χ²₃ = 16.9; P < .001).


    The epidemiologic features of PEs are more nuanced than previously thought. Research is needed that focuses on similarities and differences in the predictors of the onset, course, and consequences of distinct PEs.