Table 1.

Sample characteristics of included studies investigating the preterm behavioral phenotype.

Reference	Country	Year of birth	Age at assessment, years	Preterm group			Full-term group
				Sample size, n	Gestational age at birth, M (SD), weeks	Male, %	Sample size, n	Gestational age at birth M (SD), weeks	Male, %
Loe et al. (31)	USA	1992–1999	9–16	25	28·6 (N/R)	48	20	39·3 (N/R)	50
Taylor et al. (32)	USA	1992–1995	14	169	26·4 (2)	37	115	37 (N/R)	36
Korzeniewski et al. (33)	USA	2002–2004	10	776	<28 weeks*	N/R	–	–	–
Samuelsson et al. (34)	Sweden	1992–1998	10–15	130	24·4 (0·7)	46	103	39·4 (1·3)	51
Johnson et al. (35)	United Kingdom	2009–2010	2	638	34·9 (1·2)	54	765	39·3 (1·4)	50
Burnett et al. (36)	Australia	2005	8	181	26·8 (1·9)	57	185	39·8 (1·3)	56
Lean et al. (37)	USA	2007–2010	5	85	26·5 (1·8)	44	40	39·5 (0·8)	43

N/R, not reported. *No mean gestational age of sample reported.