Falling IQ scores in childhood may signal psychotic disorders in later life
New research shows adults who develop psychotic disorders experience declines in IQ during childhood and adolescence, falling progressively further behind their peers across a range of cognitive abilities. The researchers from King's College London's Institute of Psychiatry, Psychology & Neuroscience (IoPPN) and Icahn School of Medicine at Mount Sinai in the United States found falls in IQ start in early childhood, and suggest educational interventions could potentially delay the onset of mental illness.
Psychotic disorders, such as schizophrenia, are severe mental illnesses affecting 1-3% of the UK population that cause a range of abnormalities in perception and thinking. The study, published today in JAMA Psychiatry, is the first to track IQ scores and cognitive abilities throughout the entire first two decades of life among individuals who develop psychotic disorders in adulthood.
Dr Josephine Mollon from King's IoPPN, now with Yale University, said: 'For individuals with psychotic disorders, cognitive decline does not just begin in adulthood, when individuals start to experience symptoms such as hallucinations and delusions, but rather many years prior – when difficulties with intellectual tasks first emerge – and worsen over time. Our results suggest that among adults with a psychotic disorder, the first signs of cognitive decline are apparent as early as age 4.'
Previous studies have shown that deficits in IQ begin many years before hallucinations and delusions first appear in patients with psychotic disorders, but the timing of when these IQ deficits emerge has not been clear. The new study provides the clearest evidence to date of early life cognitive decline in individuals with psychotic disorders.
The study included 4322 UK-based individuals who were followed from 18 months to 20 years old. Those who developed psychotic disorders as adults had normal IQ scores in infancy, but by age 4 their IQ started to decline, and continued to drop throughout childhood, adolescence and early adulthood until they were an average of 15 points lower than their healthy peers.
As well as falling behind in IQ, individuals who developed psychotic disorders lagged increasingly behind their peers in cognitive abilities such as working memory, processing speed and attention.
IQ scores fluctuate among healthy individuals, and not all children struggling at school are at risk of developing serious psychiatric disorders. Senior author Dr Abraham Reichenberg, Professor of Psychiatry at the Icahn School of Medicine at Mount Sinai and with King's IoPPN said: 'It is important to bear in mind that many children will experience some difficulties with schoolwork or other intellectual tasks at some point in their lives, and only a small minority will go on to develop a psychotic disorder.'
The results suggest that adults who develop psychotic disorders do not go through a deterioration in cognitive function, but instead they fail to keep up with normal developmental processes. Early interventions to improve cognitive abilities may potentially help stave off psychotic symptoms from developing in later life.
'There are early interventions offered to adolescents and young adults with psychosis,' said Dr Reichenberg. 'Our results show the potential importance of interventions happening much earlier in life. Intervening in childhood or early adolescence may prevent cognitive abilities from worsening and this may even delay or prevent illness onset.'
The researchers are now examining changes in the brains of individuals who go on to develop psychotic disorders, as well as potential environmental and genetic risk factors that may predispose individuals to poor cognition.
The study was funded by the Medical Research Council, and the data was drawn from the Avon Longitudinal Study of Parents and Children (ALSPAC).
Notes to editors
'Course of Cognitive Development From Infancy to Early Adulthood in the Psychosis Spectrum' by Mollon et al., JAMA Psychiatry, DOI: 10.1001/jamapsychiatry.2017.4327
To contact the authors, or for further media information, please contact: Robin Bisson, Senior Press Officer, Institute of Psychiatry, Psychology & Neuroscience, King's College London, [email protected] / +44 20 7848 5377 / +44 7718 697176.
About King's College London
King's College London is one of the top 25 universities in the world (2017/18 QS World University Rankings) and among the oldest in England. King's has more than 26,500 students (of whom nearly 10,400 are graduate students) from some 150 countries worldwide, and nearly 6,900 staff. The university is in the second phase of a £1 billion redevelopment programme which is transforming its estate.
King's has an outstanding reputation for world-class teaching and cutting-edge research. In the 2014 Research Excellence Framework (REF) King's was ranked 6th nationally in the 'power' ranking, which takes into account both the quality and quantity of research activity, and 7th for quality according to Times Higher Education rankings. Eighty-four per cent of research at King's was deemed 'world-leading' or 'internationally excellent' (3* and 4*). The university is in the top seven UK universities for research earnings and has an overall annual income of more than £600 million.
King's has a particularly distinguished reputation in the humanities, law, the sciences (including a wide range of health areas such as psychiatry, medicine, nursing and dentistry) and social sciences including international affairs. It has played a major role in many of the advances that have shaped modern life, such as the discovery of the structure of DNA and research that led to the development of radio, television, mobile phones and radar.
King's College London and Guy's and St Thomas', King's College Hospital and South London and Maudsley NHS Foundation Trusts are part of King's Health Partners. King's Health Partners Academic Health Sciences Centre (AHSC) is a pioneering global collaboration between one of the world's leading research-led universities and three of London's most successful NHS Foundation Trusts, including leading teaching hospitals and comprehensive mental health services. For more information, visit: kingshealthpartners.org.
About the Medical Research Council
The Medical Research Council is at the forefront of scientific discovery to improve human health. Founded in 1913 to tackle tuberculosis, the MRC now invests taxpayers' money in some of the best medical research in the world across every area of health. Thirty-two MRC-funded researchers have won Nobel prizes in a wide range of disciplines, and MRC scientists have been behind such diverse discoveries as vitamins, the structure of DNA and the link between smoking and cancer, as well as achievements such as pioneering the use of randomised controlled trials, the invention of MRI scanning, and the development of a group of antibodies used in the making of some of the most successful drugs ever developed. Today, MRC-funded scientists tackle some of the greatest health problems facing humanity in the 21st century, from the rising tide of chronic diseases associated with ageing to the threats posed by rapidly mutating micro-organisms. http://www.mrc.ac.uk