Table 3.

Results of hierarchical multiple regression relating physical health and mental health to symptom severity and BMI

	Model 1		Model 2		Model 3		Model summary
	β	t	β	t	β	t	F	R2	ΔF	ΔR2
Physical health
Age	−0.081	−1.093	−0.116	−1.688	−0.141	−2.063*	2.252*	0.052*	–	–
Gender	−0.061	−1.052	−0.050	−0.937	−0.033	−0.611
Single and Marr†	−0.020	−0.263	0.003	0.048	−0.030	−0.439
Divo† and Marr†	−0.043	−0.697	−0.035	−0.609	−0.035	−0.621
Education	0.174	2.913**	0.150	2.725**	0.130	2.404*
IBS-C and IBS-D	0.032	0.529	0.024	0.438	−0.004	−0.081
IBS-M and IBS-D	0.048	0.775	0.003	0.049	−0.030	−0.529
Symptom severity	–	–	−0.389	−7.246**	−0.387	−7.295**	8.007**	0.200**	52.498**	0.147**
Under† and normal	–	–	–	–	−0.003	−0.060	7.965**	0.237**	4.605**	0.037**
Over† and normal	–	–	–	–	0.067	1.193
Obesity and normal	–	–	–	–	−0.177	−3.170**
Mental health
Age	0.159	2.106*	0.133	1.834	0.119	1.611	0.854	0.020	–	–
Gender	−0.029	−0.499	−0.021	−0.375	−0.006	−0.110
Single and Marr†	0.052	0.690	0.070	0.958	0.068	0.922
Divo† and Marr†	−0.020	−0.316	−0.014	−0.224	−0.007	−0.117
Education	−0.045	−0.750	−0.064	−1.092	−0.066	−1.133
IBS-C and IBS-D	0.024	0.381	0.018	0.300	0.009	0.144
IBS-M and IBS-D	0.022	0.356	−0.012	−0.194	−0.025	−0.408
Symptom severity	–	–	−0.294	−5.179**	−0.301	−5.263	4.168	0.105**	26.824**	0.084**
Under† and normal	–	–	–	–	−0.077	−1.307	3.234**	0.112**	0.772	0.007
Over† and normal	–	–	–	–	0.017	0.280
Obesity and normal	–	–	–	–	−0.041	−0.684

Model 1 factors: age, gender, family status, education status, IBS subtypes.

Model 2 factors: age, gender, family status, education status, IBS subtypes, symptom severity.

Model3 factors: age, gender, family status, education status, IBS subtypes, symptom severity, BMI categories.

IBS-U was not included in the analysis, because the sample size is too small.

Normal weight, BMI 18.5–25 kg/m²; obesity, BMI >30 kg/m²; overweight, BMI 25–30 kg/m²; underweight, BMI <18.5 kg/m².

*P<0.05; **P<0.01.

†Marr, married or unmarried cohabitation; Divo, divorced or widowed; Under, underweight; Over, overweight.

BMI, body mass index; IBS-C, irritable bowel syndrome (IBS) with constipation; IBS-D, IBS with diarrhoea; IBS-M, mixed IBS.