Characteristics of Patients with Comorbid Mental Health and Substance Use Disorders

Table 1 shows the demographic and clinical characteristics of the total sample, and for patients with COD compared to those without. Patients with COD were younger than those without COD, and more patients in the COD group had a lower education level. In addition, those with COD were more likely to have an unstable housing arrangement, and to have higher baseline and follow-up levels of mental distress. We found a significant reduction in mental distress at follow-up in both groups of patients. Moreover, the baseline motivation to change substance use behavior was as high in patients with COD as among patients without COD. With respect to types of SUD diagnoses, the results revealed that patients with COD were less likely than patients without COD to have an alcohol use disorder (F10). Patients with COD were comparatively more likely to have each of the illicit drug use disorders (i.e. cannabis use disorder, sedatives use disorder, opiate use disorder and stimulant use disorder), and polysubstance use. The data also showed that patients with COD had significantly longer treatment stays.
Table 1

Sample characteristics of patients with COD compared to patients without COD.

Variables	Total (N = 611)		COD(n = 289)		Without COD (n = 322)		COD versuswithout COD
	Na	% or mean (SD)	n	% or mean (SD)	n	% or mean (SD)	p-value	Effect size
Age (years) at intake	610	30.0 (13.9)	288	32.9 (11.6)	322	42.7 (14.1)	< 0.000	0.759
Female	175	28.7	91	31.6	84	26.2	0.139	0.060
Education level low	189	32.6	109	39.5	80	26.3	< 0.001	0.140
Unstable housing arrangement1	210	35.1	117	41.2	93	29.6	0.003	0.121
Motivation	610	4.25 (0.77)	289	4.26 (0.78)	321	4.24 (0.75)	0.663	0.027
Mental distress baseline	611	2.15 (0.71)	289	2.30 (0.69)	322	2.02 (0.70)	< 0.001	0.403
Mental distress follow-up2	425	1.93 (0.74)	206	2.07 (0.73)	219	1.79 (0.72)	< 0.001	0.386
Improved mental distress3	425	0.22 (0.79)	206	0.22 (0.79)	219	0.23 (0.80)	0.852	0.013
Length stay (days)	611	93.8 (79.6)	289	112.2 (92.2)	322	77.2 (61.9)	< 0.001	0.446
SUD diagnoses4	585	95.7
- Alcohol use F10	345	59.0	132	48.4	213	68.3	< 0.001	0.202
- Opioid use F11	111	19.0	64	23.4	47	15.1	0.010	0.107
- Cannabis use F12	216	36.9	128	46.9	88	28.2	< 0.001	0.193
- Sedative use F13	170	29.1	99	36.3	71	22.8	< 0.001	0.148
- Stimulant use F15	188	32.1	105	38.5	83	26.6	0.002	0.127
- Alcohol use only	229	39.1	62	22.7	167	53.5	< 0.001	0.315
- Polysubstance use5	134	21.9	77	28.2	57	18.3	0.004	0.118

¹Reference: Owned or rented residence. ² For both patients with and without COD, the mean score of mental distress was lower at follow up (t = 41.15, df = 205, p < 0.001, and t = 36.66, df = 218, p < 0.001, respectively). ³ Calculated by subtracting the mean follow-up score from the mean baseline score. ⁴ More than one diagnosis could be registered for each patient. The most common two-substance combination was cannabis use and stimulant use (n = 113).⁵ Three or more SUD diagnoses

Notes: Percentages in valid percent. Categorical variables presented as valid percentages (%); continuous variables presented as mean (SD). Effect size was measured using Cohen’s d and Cramer’s V, as appropriate