2.6 Statistical analyses
Potential sex and group differences in demographic and clinical
characteristics were analyzed, such as ADHD symptoms, depression,
anxiety, childhood trauma, and impulsivity. In case of significant
effects for sex, group, or sex by group interactions, these outcome
measures were included as confounders in follow-up exploratory analyses.
Potential sex and group differences in subjective cue-reactivity
(craving and affect) were analyzed using two repeated measures ANOVAs,
with cue-type (cocaine vs neutral or emotional versus neutral) as
repeated measures, group and sex as between group variable, and craving
and negative affect as outcome variables. With regards to the assessment
of affect during the cue reactivity paradigm, the current study asked
for the participants rating in affect (a negative value represented a
negative affect, a positive value reflects a positive affect). Negative
or lower scores represent an increase in negative affect, while
increases or positive scores represent an increase in positive affect.
Sex-dependent differences in negative emotional and cocaine cue
activation of the ROIs was tested using repeated measures ANOVAs. More
specifically, cue type (emotional cues versus neutral cues and cocaine
cues versus neutral cues) was included as repeated measures in two
separate analyses, group and sex as independent factors, and mean
framewise displacement (FD) as covariate of non-interest. In case of
significant sex by group by cue-type interaction effects, within group
and sex follow-up tests were performed.
In order to investigate the moderating role of cocaine use
characteristics on emotional and cocaine cue reactivity, several within
CU group repeated measures analyses were performed, with cue type
(emotional cues versus neutral cues and cocaine cues versus neutral
cues) as repeated measure in two separate analyses, mean activation in
the ROIs as dependent variable, sex as between group factor, and FD as
covariate of non-interest. The following variables were included as
covariates of interest, including years of regular cocaine use, age of
onset of regular cocaine use, cocaine use severity (DUDIT-scores), and
cocaine use per month in grams. In case of significant sex by covariate
interaction effects, within sex follow-up tests were performed.
To test for main and interaction effects of group, sex and cue type
outside the predefined ROIs, an exploratory whole-brain analysis was
performed, with mean FD values for each subject as covariate of
non-interest to account for potential motion differences. Whole brain
analyses were family-wise error (FWE) rate corrected on cluster level
(p < .05), with an initial height threshold on voxel
level of p < .001.
The methods for analyzing the influence of menstrual phase and the use
of hormonal contraceptives is described in the supplementary material.