Table 1.

Sample characteristics

	Whole sample		Boys				Girls
	N	Mean (SD)	N	Mean (SD)	Min	Max	N	Mean (SD)	Min	Max	T‐test p‐value
Mother's age at 20‐week scan (years)	1,233	26.8 (5.8)	599	26.8 (5.8)	18	51	634	26.8 (5.9)	18	43	.862
Socioeconomic status (IMD)	1,230	32.9 (20.2)	598	33.3 (20.8)	1.7	80.6	632	32.6 (19.6)	1.67	79.7	.519
Maternal depression
2.5 years	242	5.2 (5)	115	4.9 (5.1)	0	24	127	5.5 (4.9)	0	23	.391
3.5 years	812	5 (4.4)	389	5.2 (4.6)	0	24	423	4.9 (4.2)	0	19	.423
5 years	738	7.5 (7.8)	352	8.1 (8.7)	0	55	386	7 (6.9)	0	38	.046
RSA
Helper hinderer	270	3.3 (0.8)	131	3.2 (0.8)	1.1	5.8	139	3.4 (0.9)	1	5.5	.366
Novel toy	266	3 (0.8)	128	2.9 (0.75)	1.5	4.7	138	3 (0.9)	0.4	5.8	.464
Engagement	257	3..3 (0.8)	123	3.4 (0.8)	1.6	5.2	134	3.3 (0.9)	0.6	6	.301
Still face	253	2.8 (0.8)	121	2.8 (0.7)	0.6	4.6	132	2.9 (0.8)	0.7	5	.550
Repair	247	3.3 (1)	119	3.4 (0.9)	1.3	5.8	128	3.3 (1)	0.6	5.9	.421
Vagal reactivity	244	0.5 (0.6)	116	0.5 (0.6)	−0.7	2.1	128	0.4 (0.6)	−0.9	2	.320
ODD symptoms
2.5 years	245	3.2 (2.2)	123	3.3 (2.2)	0	12	126	3 (2.1)	0	12	.269
3.5 years	808	2.9 (2.5)	395	3.1 (2.5)	0	12	431	2.8 (2.4)	0	12	.035
5 years	758	2.7 (2.5)	369	2.9 (2.6)	0	12	401	2.5 (2.2)	0	12	.017
ODD irritability
2.5 years	248	1.6 (1.2)	122	1.6 (1.3)	0	6	130	1.6 (1.2)	0	6	.624
3.5 years	817	1.4 (1.4)	395	1.5 (1.4)	0	6	431	1.3 (1.2)	0	6	.035
5 years	763	1.3 (1.4)	369	1.5 (1.5)	0	6	401	1.2 (1.3)	0	6	.012
ODD headstrong
2.5 years	249	1.6 (1.3)	123	1.4 (1.3)	0	6	130	1.4 (1.2)	0	6	.136
3.5 years	816	1.5 (1.4)	395	1.6 (1.4)	0	6	431	1.4 (1.3)	0	6	.090
5 years	762	1.3 (1.4)	369	1.4 (1.4)	0	6	401	1.3 (1.3)	0	6	.063

RSA, respiratory sinus arrhythmia; ODD, oppositional defiant disorder; IMD, index of multiple deprivation. p < .05 in bold.