Table 1 |.

Neurodevelopmental conditions: summary of prevalence, sex/gender ratio, and average differences in behavioural presentation and co-occurring conditions

Neurodevelopmental conditiona	Prevalence (%)	Female to male ratio	Moderation by sex/gender		Refs.
			Behavioural presentation	Co-occurring conditions
Allb	Children: 17.8 F:12.6 M: 22.7	Children: 1:1.7	‐	F: possibly internalizing problems and later detection of some conditions more likely M: possibly co-occurring externalizing behaviours more likely	12,132,133,320
Autism	1.0	1:3	F: less RRB; better social communication, prelinguistic and linguistic functioning, cognitive flexibility and autobiographical memory M: fewer compulsions and less self-injurious behaviour; better impulse inhibition and visuospatial functioning	F: higher rates of epilepsy, endocrine problems, depression, eating problems and internalizing behaviours M: hyperactivity in childhood and externalizing behaviours more likely	15,61,78–80,94,104–106,110–119,122,123,125,126,309
ADHD	Children: 5.9c Adults: 2.8	Children: 1:2.3 Adults: 1:1.6	F: inattentive presentation more likely (childhood); fewer inhibition and cognitive flexibility problems (childhood); fewer complex attention problems (adulthood) M: hyperactive presentation more likely (childhood)	F: possibly higher rates of anxiety, depression and other internalizing behaviours; higher rates of cigarette smoking M: possibly higher rates of delinquent behaviours, ODD, conduct disorder and ASPD (adulthood)	60,72,106,129–133,320
Non-syndromic ID	All: 1.0 Children: 1.8 Adults: 0.5	Mild: 1:1.6 Severe: 1:1.2 Children: 1:1.0–2.2 Adults: 1:1.1–1.4	‐	F: depression (all ages) and dementia (later adulthood) more likely M: personality disorder and psychosis (adulthood) more likely	65,158,160,162
Fragile X syndrome	F: 0.009 M: 0.014	1:1.6	F: milder cognitive difficulties, less evident dysmorphism, and higher adaptive functioning and verbal strengths	F: typically with mild ID or borderline-to-average IQ, co-occurring learning disorder, socioemotional difficulties and psychiatric problems, and 20% have an autism diagnosis M: typically with severe ID and co-occurring ADHD, anxiety and features of autism, and 50–60% have an autism diagnosis	162–164
Communication disorders	Children: 7.7	1:1.7	F: modest advantage in language acquisition in early childhood; grammar problems in childhood and later referral to services more likely	M: higher association with medical conditions in childhood	62,141–143
Learning disorders	Lifetime: 9.7 F: 7.1 M: 12.2	1:1.7	F: literacy advantage, better verbal processing speed, working memory, conceptualization, and orthographic and visuospatial coding M: tendency for mathematical skills to be less challenging, better verbal reasoning	F: higher rates of inattentive and internalizing symptoms M: higher rates of hyperactive and other externalizing behaviours	63,144–148
Motor disorders	All: 5.0–6.0 DCD, severe: 1.5 DCD, probable: 3.0 SMD: 3.0–4.0 TS: 0.77 (adults, 0.05; M, 1.1; F, 0.3) Tic disorders: 3.0 (M, 4.1; F, 3.1)	DCD, severe: 1:2 TS and other tic disorders: 1:1.5	F: onset of tics with OCD; increase of tics during menstrual cycle; higher social impairment; tics more complex and persistent, with a later onset and a later peak of severity; in DCD, gross motor problems and higher social impact more likely M: onset of tics with rage and ADHD; in DCD, fine motor problems more likely	F: possibly higher rates of anxiety and mood disorders with tics M: possibly higher rates of ADHD and disruptive behavioural disorders with tics	64,149,150,154,157

ADHD, attention-deficit/hyperactivity disorder; ASPD, antisocial personality disorder; DCD, developmental coordination disorder; F, females; ID, intellectual disabilities; M, males; OCD, obsessive-compulsive disorder; ODD, oppositional defiant disorder; RRB, restricted and repetitive behaviour; SMD, stereotypic movement disorder; TS, Tourette syndrome.

^aDSM-5-TR or ICD-11 diagnoses.

^bADHD, autism, speech fluency disorder (stuttering), learning disorders, intellectual disabilities or any other developmental delay.

^cBest estimate for children and adolescents.