Table 3.

Some environmental risk factors for psychosis supported by meta‐analytical level of evidence in the current literature

Type of environmental risk factor	Meta‐analytical association with psychosis	Association measure type: mean (95% CI)
Parental risk factors	Parental psychosis29	RR: 7.87 (4.14‐14.94)
	Parental affective disorder29	RR: 6.42 (2.20‐18.78)
	Old paternal age30	RR: 2.22 (1.46‐3.37)[Link]
Perinatal risk factors	Complications of pregnancy31, 32, 33	OR: 2.44 (1.13‐5.26)b
	Abnormal foetal growth and development31, 32	OR: 3.89 (1.40‐10.84)c
	Complications of delivery31, 32	OR: 2.21 (1.38‐3.54)d
	Gestational influenza33	RR: 1.56 (1.05‐2.32)
	Season of birth34	OR: 1.07 (1.05, 1.08)
Social risk factors	Ethnic minority35, 36, 37	RR: 4.7 (3.3‐6.8)e
	First and second generation immigrant status38	IRR: 2.3 (2.0‐2.7)f
	Urbanicity39	OR: 2.37 (2.01‐2.81)
Later risk factors	Infections40, 41, 42	OR: 2.70 (1.34‐4.42)g
	Traumatic brain injury43	OR: 1.65 (1.17‐2.32)
	Vitamin D deficiency44	OR: 2.16 (1.32‐3.56)
	Daily tobacco use45	OR: 2.18 (1.23‐3.85)
	Cannabis heavy abuse46	OR: 3.90 (2.84‐5.34)
	Childhood trauma and adversity47	OR: 2.75 (2.17‐3.47)
	Adult life events48	OR: 3.19 (2.15‐4.75)
	Premorbid IQ49, 50	OR: 4.78 (3.19‐7.13)h

RR – risk ratio, OR – odds ratio, IRR – incidence rate ratio

^aage >55, ^bgestational age <37 weeks, ^cbirth weight <2000g, ^dincubator or resuscitator, ^eBlack African vs. White British, ^ffirst generation migrants, ^gToxoplasma gondii, ^hIQ<70. Some of these risk factors may also include a genetic component.