Hypothesis 1 predicted that meditators' scores on self-report measures of affect would be significantly more improved at the conclusion of the course than those of the nonmeditators'. This is partly reflected in the results, which indicated significant postintervention improvements in self-reported depressive symptomatology and negative affect amongst the meditators. The effect size for both of these highly-significant time by group interactions suggests that future investigations with larger sample sizes would likely detect even stronger improvements.
There was a weaker relative improvement in anxiety levels. While the meditators' Beck Anxiety Inventory (BAI) scores were significantly decreased following the intervention, this change was not significantly different to the nonmeditators'. Furthermore, the very small effect size of the time by group interaction indicates that this lack of significance was not a factor of sample size. This finding runs contrary to a large body of previous research which, using validated measures, has found mindfulness training to significantly decrease anxiety (for a review, see Grossman, 2004). It suggests that the intensive nature of the course may somehow produce different effects to the mindfulness-based interventions discussed in the literature, at least in the period immediately following the conclusion of the course. It should be reiterated here that this is the first study investigating the psychological effects of an intensive period of mindfulness practice.
Also interesting is the failure to detect the predicted postintervention improvement in positive affect amongst the meditators. Indeed, there was no significant improvement in scores on this measure for either group. This is consistent with previous research, which has suggested that mindfulness may not necessarily lead to increased positive affect, but rather may result in a mild, balanced emotional demeanour characterised by a lack of negative affect (Brown & Ryan, 2003). This is salient, as researchers may wish to take this into account when selecting measurement tools for future investigations into the relationship between mindfulness and psychological wellbeing. Ultimately, it may also inform the way we define and measure psychological health.