Introduction
Depression is common, affecting approximately 280 million people worldwide (Institute of Health Metrics and Evaluation [IHME] [
22], as cited by World Health Organization [WHO], [
44]), and serious; being a leading cause of global disability [
44]. Depression often starts in adolescence, and it is estimated that, globally, 34% of adolescents aged between 10 and 19 years are at risk of developing depression at a clinical level [
38]. Adolescent depression is associated with social dysfunction, academic difficulties) and, if untreated, recurrent episodes and increased risk of chronicity [
12,
36], further contributing to the development of lifelong mental and physical health conditions in adulthood [
41]. While cognitive-behavioural interventions are used as frontline treatments, they are rarely applied in
preventative programmes to reduce adolescent depressive symptoms [
45], as they can be resource-intensive and costly. In order to develop innovative cognitive-behavioural preventative programmes, we need to better understand the cognitive correlates and precursors of adolescent depression. Previous research [
21] has drawn on the potential of future mental imagery, the ability to imagine future images vividly, as an intervention target in preventative programmes. Hutchinson et al. [
21] investigated whether vividness of future mental imagery, both positive and negative, associated with two core symptoms of adolescent depression: negative affect and anhedonia (lack of positive affect). However, as these previous associations were limited by the study’s cross-sectional design, the present study aimed to explore the across-time associations using longitudinal data.
Mental imagery refers to the capacity to ‘see with the mind’s eye’, whereby mental representations of sensory information are constructed using internal representations (e.g. past memories and predictions of the future [
16,
23,
32]).
Emotional mental imagery refers to representations that are affective in nature or function. In adults, unhelpful emotional mental imagery, such as frequent, vivid, and distressing memories of negative life events, has been implicated in the maintenance of depression [
5], as well as several other affective conditions such as social phobia [
19] and post-traumatic stress disorder [
18]. Such unwanted memories have been reported by 44–87% of adults with depression [
2,
4,
5,
25],
30. In addition to the presence of frequent, vivid negative images, reduced vividness of positive mental imagery, especially of future events, has also been associated with depression in adults [
27,
28,
40]. Similar results have been found in adolescent populations, whereby depressed adolescents have more vivid negative memories than adolescents who have never been depressed [
24]. Looking more systematically at negative and positive imagery for past and future events, a cross-sectional study by Pile and Lau [
34] reported that adolescent depression symptoms were associated with increased vividness of negative events (past and future)
and reduced vividness of positive events (again, both past and future). These associations were in contrast to associations with anxiety symptoms, which were only associated with vivid imagery of negative past events. We recently elaborated on these associations, again in adolescents, finding differential associations between future mental imagery variables and two key symptom dimensions of depression: negative affect and anhedonia. Our data showed that increased vividness of negative future imagery
and reduced vividness of positive future imagery were associated with increased negative affect, but only reduced vividness of positive future imagery was associated with increased symptoms of anhedonia [
21].Please confirm if the inserted city and country name of Affiliation 3 is correct. Amend if necessary.This is correct, thank you
These findings are important because they have implications for developing new psychological preventative interventions. Specifically, they suggest that enhancing positive affect through generation of imagery of positive future events, along with reducing the emotional impact of negative imagery, may be a promising mechanism to reduce not only negative affect but also anhedonia in depression [
37]. Indeed, a growing body of literature shows that targeting distressing mental imagery using imagery re-scripting reduces depression in adults [
4,
43] and adolescents [
33], and that increasing the vividness of positive future mental imagery reduces symptoms of anhedonia [
3] and increases positive affect [
15] in adults with depression. However, these treatment implications may be supported further by establishing a cross-time association between mental imagery variables and depressive symptoms. As such data is currently lacking, the current study aimed to establish a directional relationship between negative and positive future imagery and negative affect and anhedonia using longitudinal data.
Drawing on the cross-sectional findings by Hutchinson et al., [
21], we made three hypotheses: (i) that increased vividness of negative future imagery at baseline would be associated with greater negative affect at follow-up, (ii) reduced vividness of positive future imagery at baseline would also be associated with greater negative affect at follow-up, and (iii) reduced vividness of positive future imagery at baseline would be associated with increased anhedonia at follow-up. We used data gathered from young people during the lockdown phases of the COVID-19 pandemic to test our hypotheses. As the pandemic presented young people with various challenges, exploring depressive symptoms (negative affect, anhedonia) as a function of mental imagery variables offers a lens for understanding individual differences at this juncture. Data were from two time-points across the first wave of lockdowns as experienced by young people in Israel. Given the first-time use of the Prospective Imagery Task (PIT) in adolescents from Israel, we also aimed to assess its factor structure, along with age and sex differences. Further understanding the specific relationships between mental imagery and negative and positive affect may bridge the gap in preventative programmes for adolescent depression.
Discussion
This study aimed to extend previous cross-sectional associations between future mental imagery variables and negative affect and anhedonia by investigating whether i) negative and positive future imagery predicted later negative affect, and ii) whether positive future imagery predicted later anhedonia. Regression analyses showed significant associations between Time1 negative future imagery and Time 8 negative affect, Time 1 positive future imagery and Time 8 negative affect, and Time 1 positive future imagery and Time 8 anhedonia. However, using three cross-lagged panel models that controlled for within-construct longitudinal stability and cross-sectional associations between negative/positive future imagery and negative affect/anhedonia at Time 1, we did not obtain any significant cross-lagged pathways. We also confirmed at each time-point, the two-factor structure of the Prospective Imagery Task in an adolescent Israeli population.
Our first set of findings replicated previous cross-sectional results in a UK sample of young people, which suggest that negative affect and anhedonia have unique cognitive correlates [
21]. These results could mean that targeting both aspects of imagery could be helpful in ameliorating two key symptoms of depression, thus adding to intervention innovation efforts. This is particularly important as current treatments of depression do not adequately treat symptoms of anhedonia, with a greater focus on alleviating negative mood than enhancing positive affect [
7,
8,
10]. Our results indicate that targeting positive future mental imagery may be an important treatment target for reducing symptoms of anhedonia in adolescents, particularly as anhedonia is predictive of poorer clinical outcomes (Pizzagalli, 2022) and increased suicidal ideation, even after depressive symptoms have been controlled for (Ducasse et al., 2018). Indeed, imagery-based treatments that increase the vividness of positive future images have been shown to increase positive affect and reduce anhedonia in depression within adult populations [
3,
14,
15]. These treatments are thought to increase positive affect by increasing positive imagery bias [
3,
15] and increasing anticipatory pleasure [
14]. Future research should investigate whether these results can be replicated in depressed adolescent populations, but potentially in other mental health problems where anhedonia is present, such as schizophrenia [
31] and eating disorders [
9].
Despite the promising bivariate and multivariate findings, findings from our cross-lagged panel models indicate that the effects of future mental imagery on symptoms of negative affect and anhedonia do not “carry” across time as trait-like precursory factors. Instead, these associations between future mental imagery variables and these core symptoms of depression appear to reflect state “in the moment” effects—although even this was limited to the earlier time-point. These data may suggest that associations between mental imagery cognitions and depression symptom dimensions emerge earlier in development, and account for later correlations between these variables. In turn, these data may point to the delivery of preventative skills training in mental imagery earlier, to modify later time/context-specific effects of mental imagery on negative affect and anhedonia. Unlike some resource-intensive cognitive behavioural interventions, research has shown that psychological interventions targeting mental imagery variables can be delivered in schools and reduce symptoms of depression, as well as increasing memory specificity and ability to imagery future events [
33]. Future research could test early intervention (prevention) studies with long follow-up periods of the course of depression symptoms.
The Prospective Imagery Task was translated into Hebrew, and we gathered data to support its two-factor structure in a population of Israeli adolescents. This factor structure is consistent with the original factor structure of the PIT [
40], as well as the factor structure demonstrated in a large UK adolescent sample [
21] and a large Chinese sample of adolescents and adults [
26]. We found that the psychometric properties of the Hebrew version of the PIT, in terms of internal consistency, were consistent with previous studies [
21,
26,
40], suggesting that the PIT can be used to measure prospective mental imagery in both English and non-English speaking samples. To our knowledge, this is the first time the PIT has been used in an Israeli sample and our results suggest that a Hebrew version of the PIT can measure prospective mental imagery in an Israeli adolescent population. Whilst the PIT demonstrated good internal consistency, we found that the test–retest reliability of the PIT subscales was poor in this study. Previous research [
26] found acceptable and good, respectively, test–retest reliability for the negative and positive subscales of the PIT, although this was over a slightly shorter duration (two months) than our study. Future studies should assess the face validity of the PIT in an Israeli sample.
We explored the effects of demographic factors on positive and negative future imagery, and negative affect and anhedonia. We found that females reported significantly greater symptoms of negative affect than males, but only at Time 1. This is consistent with previous research which found that women report more negative affect than men [
13], though this was in an adult population. Additionally, we found that females reported greater vividness for negative future events than males, but again only at Time 1. This finding is broadly consistent with previous research which found that, in adolescents, females reported less vivid positive future imagery and more vivid negative future imagery than males [
21]. Unexpectedly, we only found these sex differences at Time 1. Examining the means, it appears that negative affect and vividness of negative future imagery reduced for female participants over time, whereas negative affect increased for males over time, though these cross-time comparisons were non-significant for either females or males. These small, non-significant, changes may have closed the gap between females and males at Time 8, and with the lower power due to attrition any sex differences may have become non-significant.
The current study has some limitations. First, our sample size at baseline was small, and this suffered from additional attrition (41%). We therefore may not have had enough power to detect weaker cross-lagged paths. We also could not put all variables together in one overall model with both negative affect and anhedonia at Time 8 as outcome variables. Second, our results rely on self-report measures, particularly the PIT, which means we do not know whether images generated by participants are actually detailed and vivid; nor do we know of their content. Additionally, as our data was collected during the lockdown phases of COVID-19 pandemic, it is unclear how generalisable our findings are beyond the pandemic. It is possible that vividness ratings may have been influenced by life events related to events on the PIT, e.g. “You will have lots of fun with friends” may have been less vivid to a young person in lockdown during the COVID-19 pandemic. Third, it is unclear what effect repeated assessments of these measures have on their validity. Repeated assessments could contribute to participants repeating the same responses across time (similar to practice effects) or lead to boredom and disengagement with the task and therefore less valid responses. In this context, it is worth noting that the test–retest correlations for the different measures were generally low, which may have been due to repeated testing. Lastly, as our sample only consisted of young people from Israel, our results may not generalise more globally across ethnicities. Future research is needed to replicate these findings in larger and more diverse samples, as well as in contexts outside of lockdown restrictions.
In summary, our results indicate that symptoms of negative affect are associated with having more vivid negative future imagery and less vivid positive future imagery, and symptoms of anhedonia are only associated with having reduced vividness of positive future imagery, but these effects may be time-limited. These findings extend previous cross-sectional results and may add to the potential of targeting prospective mental imagery in prevention programmes for adolescent depression.
Summary
Adolescent depression is associated with unhelpful emotional mental imagery. Cross-sectional research has shown that symptoms of negative affect are associated with more vivid negative future imagery and less vivid positive future imagery, and symptoms of anhedonia are only associated with reduced vividness of positive future imagery. However, it is unclear whether, in adolescents, depressive symptoms temporally-predict prospective mental imagery vividness or whether prospective mental imagery vividness predicts depressive symptoms. The present study therefore aimed to establish temporal relationships between these variables using longitudinal data from a sample of 111 Israeli adolescents. Using three cross-lagged panel models, at Time 1, we extended the previous cross-sectional findings between symptoms of adolescent depression (negative affect and anhedonia) and vividness of prospective positive and negative mental imagery. Despite promising bivariate and multivariate findings, once ‘concurrent’ (across-variable, within-time) and ‘stability’ paths (across-time, within-variable) were estimated, we did not find significant cross-lag paths of earlier prospective mental imagery predicting later symptoms of depression in adolescents. However, it is worth noting that attrition was high in this study, and future research should therefore consider exploring these associations in larger, more diverse populations. Extending the cross-sectional findings suggests that targeting prospective mental imagery may be important in prevention programmes for adolescent depression.
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