Table 1 Demographic characteristics of the longitudinal study sample and P -values for group comparisons

Number of subjects

100

56

-

Scans per subject, mean (SD)

2.9 (1.1)

2.6 (1.1)

0.18

Scans at time 1

92

43

-

Scans at time 2

75

35

-

Scans at time 3

66

41

-

Scans at time 4

54

28

Total number of scans

287

147

-

Age (years), mean (SD)

18.3 (8.5)

18.9 (7.8)

0.46

Age range

3.3 to 40.6

3.4 to 41.8

-

Interscan interval, mean (SD)

2.7 (0.4)

2.6 (0.5)

0.20

Interscan interval range

1.7 to 3.9

1.6 to 4.4

-

FSIQ^a mean (SD)

100.1 (17.6)

118.2 (13.2)

<0.001

FSIQ range

53 to 138

89 to 153

-

VIQ^a mean (SD)

96.3 (21.1)

114.7 (13.2)

<0.001

VIQ range

51 to 145

87 to 151

-

PIQ^a mean (SD)

102.6 (17.9)

116.3 (14.8)

<0.001

PIQ range

62 to 140

87 to 155

-