Key messages
The available evidence does not clearly support using the STAI as a screening tool because:
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the STAI was not developed specifically for screening purposes, and no generally accepted cut-offs (threshold scores) exist;
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it tends to identify individuals with anxiety disorders, but may also incorrectly label many people who do not have anxiety;
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the included studies varied in quality, and mostly involved people from different hospital-like situations, making generalisation uncertain.
In view of these limitations, it currently seems to make more sense to use shorter questionnaires specially developed for anxiety screening instead of the STAI.
Why is early detection of anxiety disorders important?
Anxiety disorders are common yet often go undiagnosed, which can delay treatment and reduce quality of life. Screening could help identify anxiety early, especially in people who might not realise they have it. However, tests are not perfect: if they do not find anxiety in someone who does have it (a 'false negative'), they may miss the opportunity for timely treatment. Although a screening test needs to be confirmed again before a diagnosis is made, labelling someone as having suspected anxiety when they do not (a 'false positive') could lead to unnecessary worry or extra healthcare visits with further testing.
What is the State-Trait Anxiety Inventory (STAI)?
The STAI is a widely used questionnaire for measuring anxiety and has two subscales: one for state anxiety, which refers to temporary feelings of anxiety in response to a situation, and another for trait anxiety, which refers to a person’s general tendency to experience anxiety across time and situations. Each part has 20 questions. Higher scores indicate higher anxiety levels. When used for screening, a threshold (called 'cut-off') is applied: people who score at or above that level may be referred for further evaluation of possible anxiety. The STAI has been investigated as a screening tool in several studies, although it was not designed for this purpose. No generally accepted cut-offs exist, but individual studies have recommended 40 for state anxiety and 44 for trait anxiety.
What did we want to find out?
Until now, the performance of the STAI as a screening tool had not been examined in a systematic review. We wanted to see how accurately the STAI detects anxiety disorders in adults.
What did we do?
We searched for all the studies that looked at the accuracy of the STAI in detecting anxiety disorders in adults. To be eligible, studies had to compare STAI scores with results from a structured clinical interview, the most accurate available method for diagnosing anxiety. We then combined the results to evaluate the overall accuracy of the STAI, considering all possible cut-offs for both subscales (STAI-S and STAI-T).
What did we find?
We included 12 studies from 11 countries, with 2525 participants (475 were found to have an anxiety disorder). Most studies included people with a variety of specific pre-existing medical conditions. One study included people without a medical condition (the partners of cancer patients).
The combined results showed that if the STAI is administered to a group of 1000 individuals, and 153 of them have an undetected anxiety disorder:
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STAI-S ≥ 40: of 508 people scoring at or above the sum score, 127 would be correctly identified as having anxiety ('true positives') and potentially benefit from further treatment. However, the remaining 381 would be falsely classified as potentially having anxiety ('false positives') and would likely be referred for further assessment to later clarify they do not need to be diagnosed for anxiety. While this may be beneficial for some (for example, to explore other causes), it could be unnecessary for others. On the other hand, of the 492 scoring below the cut-off, 26 people with anxiety and potentially in need of treatment would be missed ('false negatives'). The remaining 466 would correctly be assigned as not having anxiety ('true negatives').
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STAI-T ≥ 44: of 463 people scoring at or above the threshold, 124 would be 'true positives' and 339 'false positives'. Among the 537 scoring below the cut-off, 29 people with anxiety would be missed ('false negatives') and 508 would be 'true negatives'.
What are the limitations of the evidence?
The studies varied in quality and were mostly done in hospital-like situations, limiting our understanding of how the STAI would perform in other groups, such as the public. Also, as the STAI wasn't developed specifically for screening, interpreting the results for this purpose is challenging.
What does this mean?
The current evidence does not clearly answer whether the STAI is a reliable screening tool for detecting anxiety disorders. The findings mainly reflect the performance in specialised clinical settings, and it is uncertain if the STAI would work in the same way in other groups. Given the ambiguous and limited evidence identified, it may be worth considering shorter tools that have been developed specifically for anxiety screening.
How up to date is this evidence?
The evidence is up-to-date as of May 2024, with included studies published from 2008 to 2023.
Read the full abstract
Anxiety disorders are highly prevalent mental health conditions, yet frequently remain undiagnosed. The State-Trait Anxiety Inventory (STAI) is one of the most widely used self-report questionnaires for assessing both momentary (state) and general (trait) anxiety severity. As it has also been considered for screening, it is essential to evaluate its accuracy in identifying undiagnosed anxiety disorders.
Objectives
To assess the diagnostic test accuracy (DTA) of the State-Trait Anxiety Inventory (STAI) for detecting anxiety disorders in adults. We specifically aimed to determine accuracy estimates for the full range of sum score cut-offs and grouped our analyses by the STAI's two subscales, State Anxiety subscale (STAI-S) and Trait Anxiety subscale (STAI-T), assessing the target condition category 'any anxiety disorder' (AAD) as well as 'generalised anxiety disorder' (GAD) as one of its specific conditions.
Search strategy
We conducted a comprehensive search in Ovid Embase, MEDLINE, PubMed-not-MEDLINE, and PsycINFO (1990 to 15 May 2024). We also screened reference lists of included studies and relevant systematic reviews.
Selection criteria
We included studies of adults that administered the STAI irrespective of mode, with no limitations on the language or number of participants. We excluded studies on adults seeking help in mental health settings or participants who were recruited specifically due to mental health symptoms in other settings. Eligible studies administered the STAI as the index test and used a structured or semi-structured diagnostic interview as the reference standard, allowing the creation of 2 x 2 contingency tables. We excluded studies following a case-control design and studies with a time lag of more than four weeks between the STAI and the reference standard.
Data collection and analysis
At least two review authors independently assessed the eligibility of articles, extracted data, and evaluated the methodological quality using the Quality Assessment of Diagnostic Accuracy Studies tool, version 2 (QUADAS-2). We applied the multiple thresholds model to obtain summary sensitivity and specificity with 95% confidence intervals (CIs) across all cut-offs (from ≥ 20 to 80). Using the multiple-threshold summary receiver operating characteristic (SROC) curve, we calculated the area under the curve (AUC) as an overall measure of accuracy.
Main results
We included 12 studies from 11 countries with a total of 2525 participants, of whom 475 had an anxiety disorder. Of these, 11 studies assessed the state anxiety subscale, STAI-S (2042 participants) and eight studies assessed the trait anxiety subscale, STAI-T (1906 participants). The diagnoses made by the reference standards were all ultimately based on criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), with the Mini-International Neuropsychiatric Interview (MINI) administered in seven studies and the Structured Clinical Interview for DSM (SCID) in five studies. Eleven studies were performed in clinical settings for a variety of specific conditions (e.g. epilepsy, pregnancy), while one study included partners of cancer patients. Most studies showed a high or unclear risk of bias and applicability concerns regarding participant selection.
In detecting AAD, summary test accuracy estimates for all cut-offs were obtained from the SROC curves, with an AUC of 0.78 (95% CI 0.75 to 0.82; 11 studies, 2042 participants) for STAI-S and 0.78 (95% CI 0.75 to 0.81; 8 studies, 1906 participants) for STAI-T. At the commonly used cut-offs of ≥ 40 for STAI-S, the summary sensitivity was 0.83 (95% CI 0.77 to 0.88) and specificity was 0.55 (95% CI 0.45 to 0.65). Similarly, for STAI-T at the cut-off of ≥ 44, the summary sensitivity was 0.81 (95% CI 0.75 to 0.86) and specificity was 0.60 (95% CI 0.44 to 0.74).
The analysis of STAI's accuracy in detecting GAD was restricted by the small number of studies (STAI-S: four studies, 1182 participants; STAI-T: three studies, 988 participants). For STAI-S at the cut-off ≥ 40, the summary sensitivity was 0.86 (95% CI 0.74 to 0.93) and the specificity was 0.53 (95% CI 0.37 to 0.69). The AUC was 0.80 (95% CI 0.74 to 0.86). For STAI-T at the cut-off ≥ 44, sensitivity was 0.86 (95% CI 0.72 to 0.94) and specificity 0.57 (95% CI 0.36 to 0.75). The AUC was 0.81 (95% CI 0.79 to 0.82).
Authors' conclusions
The currently available evidence does not allow a confident judgment on the STAI's accuracy in screening for anxiety disorders. Findings come from a limited number of studies, most at high or unclear risk of bias, and almost exclusively conducted in specialised clinical settings among individuals with a variety of underlying health conditions, thus limiting generalisability. Based on common interpretations of the AUC, the overall accuracy of the STAI-S and STAI-T subscales across all cut-offs is moderate and broadly comparable to other anxiety questionnaires. While proposed cut-offs (≥ 40 for STAI-S and ≥ 44 for STAI-T) provide adequate sensitivity, specificity remains low, thus raising concerns about substantial misclassification, particularly in low-prevalence contexts. Its suitability for screening is further limited by its original purpose as a severity measure, its considerable length compared to alternative questionnaires, its two separate subscale scores without clear screening guidance, and the absence of evidence-based cut-off recommendations. Thus, the STAI currently does not appear to be the first-choice screening instrument, particularly given the availability of shorter, better-researched questionnaires that have been specifically developed for anxiety screening. However, given the limited evidence base and the lack of formal comparisons with other questionnaires, this conclusion remains preliminary.
Funding
This Cochrane review was funded by the German Federal Ministry of Education and Research (Grant Number: 01KG2105).
Registration
Protocol (2022) available via doi.org/10.1002/14651858.CD015292
