Table 3. PHQ-9 scores at pre- and post-treatment for the pooled sample and each service, subdivided into non-depressed (‘No dep’) and depressed (‘Current dep’) at entry to treatment.

Sample	Pre-treatment		Post-treatment		Mean difference	95% CI	Cohen’s d
	M	SD	M	SD
Pooled	10.75	6.18	7.81	6.08	2.94***	[2.69, 3.20]	0.48
No Dep	5.36	2.54	4.38	3.32	0.98***	[0.75, 1.22]	0.33
Current Dep	15.47	4.29	10.81	6.36	4.66***	[4.26, 5.06]	0.86
Swallowa	9.87	6.10	8.37	6.19	1.5**	[0.63, 2.37]	0.24
No Dep	4.92	2.81	5.19	3.75	− 0.27	[− 1.09, 0.56]	− 0.08
Current Dep	15.24	3.65	11.82	6.49	3.42***	[1.95, 4.89]	0.65
Robina	10.56	6.23	6.83	5.79	3.73***	[3.21, 4.25]	0.62
No Dep	5.30	2.42	4.33	3.80	0.97***	[0.48, 1.45]	0.31
Current Dep	15.47	4.44	9.16	6.34	6.30***	[5.53, 7.08]	1.16
Jackdawa	9.15	5.52	6.88	5.51	2.27***	[1.93, 2.61]	0.41
No Dep	5.37	2.58	3.95	2.74	1.43***	[1.15, 1.70]	0.53
Current Dep	14.56	3.86	11.08	5.76	3.48***	[2.79, 4.17]	0.71
Woodpeckera	12.84	6.49	10.87	6.64	1.96***	[1.34, 2.59]	0.30
No Dep	5.36	2.54	5.07	3.30	0.29	[− 0.51, 1.08]	0.10
Current Dep	16.45	4.36	13.68	6.00	2.78***	[1.96, 3.59]	0.53
Blackbirda	13.28	5.95	9.03	6.26	4.25***	[3.52, 4.98]	0.70
No Dep	6.09	2.38	4.83	2.87	1.27**	[0.47, 2.06]	0.48
Current Dep	15.89	4.53	10.56	6.46	5.34***	[4.43, 6.24]	0.96

Where post-treatment PHQ-9 data were missing, the pre-treatment PHQ-9 value was carried forward

^aPairwise comparisons were used to compare the pre- to post-treatment change in PHQ-9 scores between services (using Tukey HSD adjustment). There were differences between Robin and Swallow, Jackdaw, and Woodpecker, as well as between Blackbird and Swallow, Jackdaw and Woodpecker. In summary, Robin and Blackbird did not differ from one another in PHQ-9 reduction across their whole samples, and in both cases showed significantly larger pre-post treatment change than Swallow, Jackdaw and Woodpecker

**p < .01; ***p < .001