اثرات تمرینات تصویرسازی ذهنی به بهترین روش ممکن خود بر روی نگرشهای خلق و خوی و ناکارآمد

Dispositional optimism has been related to positive physical and mental health outcomes, increased positive mood ratings and cognitions about the future. In order to determine the causal relation between optimism and mood and cognitions optimism should be manipulated experimentally. The current study tested the effects of a best-possible-self mental imagery exercise on affect and mood ratings and dysfunctional cognitions following a sad mood induction in undergraduate students (N=40). Participants in the experimental condition wrote about their best possible self in the future for 15 min and engaged in a mental imagery task about their best possible self in the future for 5 min in order to experimentally induce optimism. Participants in the control condition wrote about a typical day for 15 min and engaged in mental imagery about a typical day for 5 min. We assessed affect, mood and dysfunctional cognitions before and after the experimental manipulation. Participants in the experimental condition had higher positive mood ratings and higher positive affect compared to participants in the control condition. Participants in the control condition reported decreased dysfunctional cognitions whereas dysfunctional cognitions in the experimental group remained unchanged. Future studies should replicate these findings in clinical groups with more profound levels of negative affect and dysfunctional cognitions.

Cognitive theories of depression emphasize the role of dysfunctional cognitive processing in the development and maintenance of depression (Beck, 1964 and Abramson et al., 1978). In Beck's cognitive model of depression, negative beliefs about the self, the world, and the future are at the core of depression, whereas the reformulated learned helplessness theory emphasizes the importance of a pessimistic attributional style, defined as interpreting negative events as internal, stable, and global. Numerous studies have shown that depressed individuals are characterized by increased dysfunctional attitudes (Haaga et al., 1991), whereas relatively fewer studies have investigated the impact of positive biases such as increased optimism about the future (Taylor and Brown, 1988) on mood and dysfunctional cognitions. Optimism can be defined as a tendency for generalized positive outcome expectancies in the future (Carver et al., 2010). Previous studies have established positive relations between optimism and physical and mental health outcomes (Segerstrom et al., 1998, Taylor et al., 2000 and Rasmussen et al., 2009). For example, Segerstrom et al. (1998) found that dispositional and situational optimism was related to more positive mood ratings and more positive immune parameters in college students. Moreover, longitudinal studies have shown that increased optimism is related to a lower incidence of depression symptoms (Giltay et al., 2006). While these studies suggest that there is a positive relation between optimism and mental and physical health, the correlational design of these studies does not allow for any causal interpretations of the relation between optimism and outcomes. In order to establish a causal relation optimism needs to be manipulated experimentally. It has been shown previously that the vividness of positive mental imagery of the future is associated with optimism, suggesting that imagery exercises are a powerful way to increase optimism and thereby mental wellbeing (Blackwell et al., 2013). In line with this, previous experimental studies that used imagery exercises to induce optimism found that imagery of positive future events indeed increased optimism and positive mood ratings (Sheldon and Lyubomirsky, 2006, Peters et al., 2010 and Meevissen et al., 2011). Moreover, one previous study has shown that a negative mood induction decreases optimism in women, suggesting that the relation between mood and optimism is bi-directional (Lewis et al., 1995). Meevissen et al. (2011) investigated the effects of daily practicing a positive future imagery exercise over a period of 2 weeks on participants' mood. In this study participants were instructed to imagine themselves in the future when everything has turned out in the best possible way. It was shown that the imagery exercise led to increased optimism already after the first session and at the 2 week follow-up assessment (Meevissen et al., 2011). While previous studies suggest that optimism has a positive effect on mood, the impact of optimism on negative cognitions remains unclear. One way to study the impact of optimism on dysfunctional cognitions in healthy participants is to trigger dysfunctional cognitions by means of a negative mood induction paradigm. Previous studies have shown that mood induction paradigms reliably increase negative mood (Martin, 1990) and trigger dysfunctional thinking patterns in people vulnerable for depression (Miranda et al., 1990 and Scher et al., 2005). Yet, to the best of the authors' knowledge, no published study to date has addressed the impact of optimism on mood or dysfunctional attitudes following a sad mood induction procedure. Thus while previous studies have shown that optimism has an effect on positive affect (e.g., Peters et al., 2010), it remains unclear whether optimism can reinstate positive affect following a sad mood induction. The aims of the current study were to replicate and extend previous findings by studying the effects of a best-possible-self (BPS) mental imagery exercise on affect, mood and dysfunctional cognitions in healthy participants that were experimentally set into a negative mood state. Previous studies have already shown that the BPS exercise reliably increases optimism (Peters et al., 2010, Meevissen et al., 2011, Hanssen et al., 2013 and Peters et al., 2013). To the best of the authors' knowledge the current study is the first to test the effects of the BPS exercise on the reinstatement of positive affect, mood and dysfunctional attitudes following a sad mood induction. We hypothesized that (1) following a sad mood induction, participants in the BPS condition would report higher levels of positive affect/mood and lower levels of negative affect/mood compared to participants in the control condition. Moreover, we hypothesized that (2) following a negative mood induction, participants in the BPS condition report lower levels of dysfunctional attitudes, compared to participants in the control condition, as measured by the dependency and perfectionism subscales as well as by the total score of the Dysfunctional Attitudes Scale.

3.1. Baseline characteristics Participants who were randomized to the experimental condition did not differ from participants randomized to the control condition with respect to age (Mean age control group: 22.2, S.D.=3.43; Mean age experimental group: 22.0, S.D.=4.30; (t(39)=−0.16, p=0.87)), baseline scores on the four mood scales (all p-values >0.05) or on the positive and negative affect scales (all p-values >0.05). Gender was equally distributed among the two conditions χ² (1, N=40)=2.5, p=0.14. 3.2. Mood induction manipulation check First, mood and affect ratings before the negative mood induction paradigm were compared to mood and affect ratings following the negative mood induction paradigm to check whether the manipulation was effective. The results of the paired sample t-test are summarized in Table 1. There was a statistically significant decrease on all mood scales following the negative mood induction, indicating that mood decreased on average following the negative mood induction. Moreover, there was a statistically significant decrease in positive affect (t(39)=−6.18, p<0.001) whereas negative affect remained stable (t(39)=−0.02, p=0.98). Table 1. Mean change in mood and positive and negative affect following the mood induction. Parameter Before mood induction After mood induction t (39) M (S.D.) M (S.D.) Mood scales Positive–negative 21.95 (14.49) 44.08 (16.81) 8.46** Glad–dull 31.90 (15.99) 53.87 (17.49) 7.16** Secure–anxious 29.50 (15.99) 39.07 (17.88) 2.71* Happy–sad 22.05 (15.73) 48.68 (18.52) 8.53** PANAS Positive affect 67.46 (12.55) 53.80 (16.41) 6.18** Negative affect 20.87 (16.63) 20.84 (17.64) 0.02 PANAS=Positive Affect Negative Affect Schedule; range scores 0–100; higher scores on the mood scales represent more negative mood; higher scores on the positive affect scale of the PANAS represent more positive affect whereas higher scores on the negative affect scale of the PANAS represent more negative affect. ⁎ p<0.05. ⁎⁎ p<0.01. Table options Next we conducted a time×condition repeated measure ANOVA on each mood scale and on the positive affect and negative affect scales from pre-mood induction to post-mood induction with condition as between subject factor. For all mood scales we found significant interactions between the within subject factor time and the between subject factor condition, except for the secure–anxious scale (positive–negative: F(1, 38)=7.08, p=0.01; glad–dull: F(1, 38)=6.10, p=0.02; happy–sad: F(1, 38)=7.64, p=0.01). Inspection of the profile plots of the significant interactions revealed that participants in the experimental condition on average experienced a stronger decrease in mood following the sad mood induction compared to participants in the control condition. For the PANAS the interaction between the within subject factor time and the between subject factor condition was not significant for the negative affect scale (F(1, 38)=0.82, p=0.37) or the positive affect scale (F(1, 38)=0.97, p=0.33) indicating that the effect of the mood induction on affect did not differ between participants randomized to the experimental or control condition.