Prenatal and perinatal factors associated with future psychosis

Although prenatal and perinatal insults are generally assumed to contribute to the etiopathogenesis of psychotic disorders, the magnitude of the association remains unclear. A study published in The Lancet explored which and to what degree prenatal and perinatal factors are associated with later onset of psychosis.

Methods
The systematic review and meta-analysis included a multistep literature search that resulted in the inclusion of 152 studies relating to 98 risk or protective factors.  The authors identified cohort and case-control studies examining the association between prenatal and perinatal factors and any International Classification of Diseases (ICD) or Diagnostic and Statistical Manual of Mental Disorders (DSM) non-organic psychotic disorder with a healthy comparison group. 

Findings
The authors found several significant risk factors. Among them were age of the parents:  maternal age younger than 20 years (OR 1.17) and 30-34 years (OR 1.05) and paternal age younger than 20 years (OR 1.31 and older than 35 years (OR 1.28). Parental psychosis was also a significant factor: maternal (OR 4.60) and paternal (OR 2.73) psychopathology, maternal psychosis (OR 7.61) and affective disorder (OR 2.26). Three or more pregnancies also represented a significant factor (OR 1.30). A suboptimal number of antenatal visits wase significant (OR 1.83). 

Maternal health issues unsurprisingly were associated with significant elevation in risk as well: herpes simplex 2 (OR 1.35), unspecified maternal infections (OR 1.27), maternal stress (OR 2.40), any famine or nutritional deficits in pregnancy (OR 1.40) or maternal hypertension (OR 1.40). Timing of the pregnancy also was a factor with increased risks for births in the winter (OR 1.05) and winter to spring (OR 1.05) season in the northern hemisphere. 

Obstetric complications, such as hypoxia (OR 1.63), ruptured (OR 1.86) and premature rupture (OR 2.29) of membranes, polyhydramnios (OR 3.05), and definite but not specified (what does definite but not specified mean?  I would leave it out) complications (OR 1.83) all were significant risk factors. Infant birthweight < 2000 g (OR 1.84), < than 2500 g (OR 1.53) or 2500-2999 g (OR 1.23) were significant factors, and birth length < 49 cm (OR 1.17) was also significant. Small for gestational age (OR 1.40), premature birth (OR 1.35) and congenital malformations (OR 2.53) were significant. 

The authors noted a few significant protective factors including: maternal age 20 to 24 years (OR 0.93) and 25 to 29 years (OR 0.92), nulliparity (OR 0.91) and birthweight 3500 to 3999 g (OR 0.90) or > 4000 g (OR 0.86).

Conclusions
The authors believe their findings indicate that several factors are significantly associated with future psychosis and that they could help improve understanding of psychosis pathogenesis, enhance risk prediction, and better inform preventive strategies.