Low birth weight or preterm babies have an increased risk of personality disorders


Events that occur immediately before and after birth (perinatal factors) can often have a significant impact later in life. Research has shown that the risk of many mental health and neurological conditions (schizophrenia, ADHD, depression, autism and eating disorders) increases when complications occur around this time.

However, there have been relatively few studies to date that have explored the associations between perinatal risk factors and personality disorders, and the studies that have been published show a mixed and often conflicting picture.

A research team from Oxford and Stockholm have recently published a new study that looks at this very issue, using data from several nationwide population-based registries in Sweden. The authors identified 150 individuals with personality disorder (85% male, with an average age of 20) and compared them with two separate control groups:

  1. 97 individuals without any psychiatric disorder (a nested case-control), identified from a larger group of 732 people on the Swedish registers
  2. 1,498 individuals (matched by age and gender) with no history of psychiatric hospitalisation (a population-based case-control)

Information on risk factors was taken from the Swedish Medical Birth Register, which represents 99% of all births in Sweden.

The authors undertook a logistical regression analysis to compare the chances of exposure to perinatal factors in people with personality disorders and the control groups, and attempt to deal with confounders including the samples from which the cases and controls were drawn.

Here’s what they found:

  • Low birth weight and immaturity were significantly associated with personality disorder in both arms of the study
  • Small gestational age, asphyxia and anoxia and small head circumference were also found to be significant in the population-based study
  • Pre-term birth (<37 weeks) was significantly associated with personality disorder in both arms of the study
  • Young maternal age, delivery complications and maternal parity of three or more were also found to be significant in the population-based study

This kind of case-control study can never prove a causal link between perinatal risk factors and personality disorders, but it can add to what we know about this under-researched area. One possible explanation that the authors consider in their conclusion is the fact that perinatal complications may lead to abnormal brain development and function. They welcome more research in this area.


Fazel S, Bakiyeva L, Cnattingius S, Grann M, Hultman CM, Lichtenstein P, Geddes JR. Perinatal Risk Factors in Offenders with Severe Personality Disorder: A Population-based Investigation. J Pers Disord. 2012 Aug 1. [Epub ahead of print] [PubMed abstract]

Premature babies have greater risk of serious mental illness. The Mental Elf, 6 Jun 2012.

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Andre Tomlin

André Tomlin is an Information Scientist with 20 years experience working in evidence-based healthcare. He's worked in the NHS, for Oxford University and since 2002 as Managing Director of Minervation Ltd, a consultancy company who do clever digital stuff for charities, universities and the public sector. Most recently André has been the driving force behind the Mental Elf and the National Elf Service; an innovative digital platform that helps professionals keep up to date with simple, clear and engaging summaries of evidence-based research. André is a Trustee at the Centre for Mental Health and an Honorary Research Fellow at University College London Division of Psychiatry. He lives in Bristol, surrounded by dogs, elflings and lots of woodland!

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