. 2010 Dec 1;33(12):1693–1702. doi: 10.1093/sleep/33.12.1693

Table 2.

Pearson correlation coefficient among insomnia subtypes: 2003

Insomnia subtype	DIS	EMA	DMS
DIS	–	0.383^*	0.309^*
EMA	0.282^*	–	0.358^*
DMS	0.248^*	0.321^*	–

Numbers in the upper triangle are based on all participants (N ≅ 4,000). Numbers in the lower triangle are based on participants without depression (N ≅ 3,050).

DIS refers to difficulty initiating sleep; EMA, early morning awakening; DMS, difficulty maintaining sleep.

Statistically significant at 0.01 level.