Toward a unified understanding of climate anxiety: Examining measures of climate and eco-anxiety

PLOS One | https://doi.org/10.1371/journal.pone.0339562 December 29, 2025 3 / 19 because researchers may believe they are studying distinct phenomena when they are not [14,15]. Clarifying whether climate anxiety and eco-anxiety are truly distinct is therefore essential. For both climate and eco-anxiety, there is one dominant scale each. Interestingly, both two scales are used in research examining the psychological impacts of climate change (e.g., in this meta-analysis by Kühne and colleagues, [5]). A recent review by Jarrett and colleagues [16] identified several other measures with similar item content or construct names, such as the Climate Change Worry Scale [CCWS; 17], the Environmental Worry Questionnaire [EWQ; 18], or the Climate Change Distress and Impairment Scale [CC-DIS;19], among others. However, Jarrett and colleagues [16] also highlight that the Climate Anxiety Scale [CAS; 6] and the Hogg Eco-Anxiety Scale [HEAS; 12] are the most frequently used mea- sures in the field, which is why we focus on these two scales in this work. The Climate Anxiety Scale (CAS) was originally developed by Clayton and Karazsia [6] to capture a “clinically signifi- cant anxious response to climate change” (p. 9). While the initial development included a broader set of items and factors, the final CAS comprises two factors: cognitive–emotional impairment and functional impairment. However, the German version [9] identified a different two-factor structure—behavioral symptoms and cognitive consequences—excluding one

item. These two factors differ from those found in Clayton and Karazsia’s [6] original validation. Since the original factor structure has been difficult to replicate in many studies [for an overview, see 20], there is ongoing debate about the CAS measurement model. Furthermore, contradicting the existing debate on measurement models, some studies have used the CAS as a unidimensional construct, justified by the high correlation of the factors [21–23]. The CAS has also been crit- icized for not capturing the emotional core of climate anxiety, which some argue distinguishes it from other emotions [9]. The Hogg Eco-Anxiety Scale (HEAS; [12]) was developed to measure the broader construct of eco-anxiety, encom- passing anxiety related not only to climate change but also to other environmental crises. However, this broader context is primarily reflected in the instructions of the HEAS, which ask respondents how often they have been bothered by the fol- lowing problems over the last two weeks when thinking about climate change and other environmental concerns, such as species extinctions, ozone hole or ocean pollution. The actual items of the scale, however, rarely mention climate change or other environmental concerns and largely focus on possible impairments across four factors: i) affective symptoms (aiming at overcoming a CAS shortcoming), ii) rumination, iii) behavioral symptoms, and iv) anxiety about one’s negative impact on the planet. While the four-factor structure of the HEAS has been successfully replicated [20], the high correla-

tions between factors have led some researchers to adopt a more parsimonious single-factor model in practice [24,25]. Studies evaluating both scales together revealed a significant overlap, evident from high correlations between the scales (r = .58–.69, depending on the subscales;[20]). However, these correlations have been examined only at the man- ifest level (i.e., using aggregated scale scores). Given that measurement error attenuates correlations between aggre- gated scores [26] and considering the imperfect internal consistency of the scales (e.g., as reflected in their Cronbach’s alphas), the true correlation between climate anxiety and eco-anxiety is likely even higher. Thus, to assess the constructs’ distinctiveness, disattenuating approaches, such as latent variables from confirmatory factor analyses or structural equa- tion modeling, should be used. These approaches account for measurement errors and allow researchers to examine how much variance is shared between constructs, regardless of differences in their operationalization. Applying these methods can clarify whether the constructs measured by the CAS and HEAS are truly distinct or whether they largely capture the same overarching phenomenon, warranting reconsideration of separate scales. While both the CAS and HEAS have been subject to some validation efforts, broader validation within a nomological network of related traits remains limited. Both scales assess psychological responses to environmental concerns but differ

in scope and focus. The CAS primarily measures cognitive and functional impairments associated with climate change– related distress, while the HEAS captures a broad range of responses, including rumination, behavioral symptoms, and anxiety about one’s environmental impact. Although both scales assess aspects of distress comparable to clinically relevant psychological symptoms, their validity has been evaluated mostly by correlating them with self-rated symptoms of depression and anxiety. These studies were conducted in general populations and non-clinical samples, which typically