Table 2.

Descriptive statistics of primary and significant secondary outcomes, effect sizes, and p values

Outcome	Time	Group	n	Mean	Median	SD	Min	Max	Cohen’s d	p	Effect size
Approach behavior BAT in vivo	Baseline	Placebo	26	3.96	4.00	1.40	1.00	6.00
	Baseline	VPA	22	3.77	3.50	1.31	1.00	6.00	−0.14
	Follow-up	Placebo	26	5.23	5.00	2.12	1.00	8.00
	Follow-up	VPA	22	5.41	5.00	1.53	2.00	8.00	0.10
	Difference score	Placebo	26	1.27	1.00	1.80	−2.00	6.00
	Difference score	VPA	22	1.64	1.50	1.50	−1.00	5.00	0.22	0.46	d = 0.23
FSQ	Baseline	Placebo	26	70.62	70.50	16.74	37.00	97.00
	Baseline	VPA	22	72.68	71.00	14.08	45.00	99.00	0.13
	Follow-up	Placebo	26	49.54	50.00	25.53	3.00	86.00
	Follow-up	VPA	22	34.09	30.00	17.97	6.00	75.00	−0.69
	Difference score	Placebo	26	−21.08	−14.00	21.74	−72.00	20.00
	Difference score	VPA	22	−38.59	−36.50	15.34	−66.00	−5.00	−0.92	0.003	d = −0.95
SBQ	Baseline	Placebo	26	54.84	59.58	19.85	4.17	90.54
	Baseline	VPA	21a	55.45	51.35	11.96	31.04	77.71	0.04
	Follow-up	Placebo	26	43.94	47.92	22.38	0.83	80.42
	Follow-up	VPA	22	31.38	31.88	16.00	10.63	71.88	−0.64
	Difference score	Placebo	26	−10.89	−10.64	12.75	−44.63	9.17
	Difference score	VPA	21a	−24.53	−22.50	15.49	−54.17	0.52	−0.97	0.002	d = −1.02

Note: VPA, valproic acid; FSQ, Fear of Spiders Questionnaire (sum score ranges from 0 to 108); SBQ, Spider Phobia Beliefs Questionnaire (mean sum score ranges from 0 to 100); SD, standard deviation; min, minimum; max, maximum; Cohen’s d refers to effect size calculated based on mean values, p refers to p value of main effect of group allocation in the used statistical model, i.e., difference between follow-up and baseline. Effect size refers to effect size of main effect of group allocation in the used statistical model, i.e., statistical model including age and sex as covariates (for more information, see the supplementary information).

^aSBQ was not collected for one participant at baseline.