Family structure and posttraumatic stress reactions: a longitudinal study using multilevel analyses

BMC Psychiatry

Table 2 Intra-class correlations for posttraumatic stress reactions, with and without adjustments for predictors at 6 (T₁) and 24 (T₂) months post-tsunami, and differences between these times

	Without adjusting for predictors (95% CI) ^a			Adjusting for predictors (95% CI) ^b
	T₁	T₂	Difference (T₂-T₁)	T₁	T₂	Difference (T₂-T₁)
Unexplained variance between households	0.38	0.33	-0.05	0.23	0.17	-0.06
Unexplained variance between individuals within households	0.33	0.37	0.04	0.18	0.32	0.14
Intra-class correlation	.53 (.36, .62)	.47 (.45, .68)	-.06 (-.24, .10)	.56 (.42, .69)	.35 (.17, .52)	-.21 (-.43, .005)
Change in unexplained variance between households when including predictors				-44.8%	-48.4%
Change in unexplained variance between individuals within households when including predictors				-36.0%	-9.0%
Total change in unexplained variance when including predictors				-41.3%	-28.2%

Adjustment for mutual household is done by mixed method with mutual household as intercept. Dependent variable is mean posttraumatic stress reactions (IES). Intra-class correlation (ICC) is defined as the proportion of unexplained variance that is between groups (possible range 0-1). It is calculated as unexplained variance between households divided by the sum of unexplained variance between and within households. Predictors controlled for include witnessed abandoned children, witnessed multiple dead bodies, caught or chased by waves, death of family member or friend, immediate response of fear, and immediate response of helplessness.
Difference (T₂-T₁) is the difference between the two assessment points in unexplained variance and intra-class correlation.
Change in variance in analyses adjusted for predictors is the change in unexplained variance when taking into account the predictors in percentage of unexplained variance before taking into account any predictors. The percentages are different from what can be calculated from the first part of the table because the change in unexplained variance is based on models excluding participants with missing data on predictor variables (N = 550).
^a N = 641. ^b N = 550.

ISSN: 1471-244X