2.1. Search Strategy

A search was conducted for published literature in Medline, PsycInfo, CINAHL Complete and International Pharmaceutical Abstracts. Studies published until September 2023 were included, with no lower date limit applied. Keyword search terms and MeSH headings were used to conduct the search. However, LTCs were intentionally excluded as a keyword or MeSH heading because of the scarcity of relevant studies specifically labelled under this term. Instead, studies related to LTCs were identified through manual screening. No further restrictions were applied to the search process. Reference lists were hand-searched for additional relevant studies. Grey literature was identified through targeted searches of dissertations/theses and conference abstracts. An example search strategy for the PsycInfo database can be found in Supporting Information 1.

2.2. Inclusion and Exclusion Criteria

This scoping review considered a broad range of published literature, including systematic reviews, observational studies, clinical trials, case studies, research protocols and any other relevant studies. We also considered grey literature, dissertations, discussion papers, government reports, expert opinions, position papers and other texts as they could potentially be relevant to the review’s objectives.

Studies were eligible for inclusion if they included adults (≥18 years) with at least one LTC. LTCs were defined as any ongoing, recurring or long-term physical conditions that can significantly impact people’s lives, including but not limited to, diabetes, cardiovascular diseases, respiratory diseases and cancers. Only studies conducted in primary care settings were included, defined as settings with no/limited specialist involvement. sDep and sAnx (or similar terms—subclinical or subsyndromal) were defined as signs and symptoms of depression and anxiety that do not meet the diagnostic criteria for a clinical diagnosis of depression and anxiety. Articles that explicitly referred to subthreshold, subclinical or subsyndromal depression and anxiety, even when no diagnostic interview had been conducted were included. This includes also studies that reported the non-pharmacological interventions for sDep and sAnx, and studies involving the identification of sDep and sAnx, regardless of whether it was the main study aim. Any studies that involved the identification of sDep/sAnx were included, irrespective of whether the study included an intervention component.

Any depressive and anxiety disorders meeting the diagnostic criteria and any other terms not stating subthreshold, subclinical or subsyndromal were excluded from the review.

2.3. Study/Source of Evidence Selection

Following the literature search, all identified articles from the different databases were uploaded into a reference management software (Endnote). Rayyan software [20] was used to screen studies and duplicates were removed using this software.

Two of the authors (Patrick Cabasag and Jeff Harrison) independently screened study titles and abstracts during the initial search. The inclusion criteria related to LTCs and adults aged 18 years and above were not applied during preliminary screening, as these characteristics were challenging to discern from titles and abstracts alone. Following the initial screening, Patrick Cabasag and Jeff Harrison reviewed the full-text articles to ensure they met all the specified inclusion criteria. Any differences in opinions between the authors were resolved through consensus.

Pilot testing of 25 randomly selected articles was conducted at the beginning of the study for quality assurance, as per JBI recommendation [17]. Patrick Cabasag, Jeff Harrison and Lauren Shepherd independently screened the titles and abstracts of these 25 articles and included studies based on the predefined inclusion and exclusion criteria. Patrick Cabasag, Jeff Harrison and Lauren Shepherd discussed any discrepancies and updated the inclusion/exclusion criteria as needed. Title and abstract screening only continued once a 75% or greater agreement was achieved.

2.4. Data Extraction/Charting

Data relevant to the review objectives were collected from the included studies using a data extraction form (Supporting Information 2). The extracted data included the title, authors, year of publication, objectives, study design and population, condition(s) studied, identification/screening methods, description of treatments/interventions and other key findings. For studies without an intervention component, the study designs were not extracted as they were not relevant to our review’s objectives, but the definitions and instruments used were still considered relevant.

Following guidance from the JBI Manual [17], Patrick Cabasag and Lauren Shepherd piloted the data extraction form using three methodologically varied articles from the included set to confirm its suitability for capturing all relevant information for this scoping review. Any necessary modifications to the form were made through discussions between Patrick Cabasag and Lauren Shepherd. Data extraction was independently carried out by both authors (Patrick Cabasag and Lauren Shepherd), with a subsequent check performed by Patrick Cabasag.

3.1. Characteristics of Included Studies

Studies included in the review were mostly related to sDep, with only four studies related to sAnx [21–24].

3.2. Identification of sDep and sAnx

A summary of the conceptualised definitions of sDep and sAnx, as stated in the introduction of the included studies, is presented in Table 3.

Depressive and anxiety symptoms were primarily identified using various screening tools. In some studies, diagnostic interviews were used to exclude a mental health disorder diagnosis. The patient health questionnaire (PHQ) was the predominant screening tool, utilised in five studies [25, 27, 33, 35, 36]. Other tools employed included the Centre for Epidemiologic Studies Depression Scale (CES-D) [22, 24], hospital anxiety and depression scale (HADS) [24, 30], Whooley questionnaire[34], Beck depression inventory (BDI) [32], global assessment score (GAS) [28], and the General Health Questionnaire (GHQ) [21].

Regarding methodological details, six studies relied on self-report measures, using specific scores to determine if participants had sDep and sAnx [25, 27, 30–33]. Eleven studies used diagnostic interviews to identify sDep and sAnx and exclude major depression [21–24, 26, 28, 29, 34–36, 48]. Of these, eight administered the diagnostic interview after the complementary use of a screening tool [21, 22, 24, 26, 28, 34–36]. Most studies referred to the Diagnostic and Statistical Manual of Mental Disorders (DSM), with one study utilising the international classification of diseases (ICD) [31].

In terms of interview administration, trained researchers or research assistants commonly conducted the diagnostic interviews. Other interviewers included psychiatrists and psychologists.

In studies incorporating an intervention component for sDep and sAnx, a diagnostic interview was consistently utilised. Most adopted the Mini International Neuropsychiatric interview (MINI) [21, 22, 24, 34, 35, 48], while one study used the Structured Clinical Interview for DSM Disorders (SCID) [36]. The purpose of these diagnostic interviews was to identify sDep and sAnx and exclude a clinical mental health disorder diagnosis. Moreover, five of these studies used diagnostic interviews according to DSM IV criteria [22, 24, 34–36]. The operational definitions and screening tools used across studies are presented in Tables 1 and 2.

3.3. Management of sDep and sAnx

Of the reviewed studies, seven incorporated an intervention component for managing sDep and sAnx. Notably, six of these studies were RCTs [21, 22, 24, 34–36], and one was a feasibility study [48]. The interventions included a collaborative care (CC) model, stepped-care models, psychotherapy interventions and other additional components. Regarding the psychological interventions, four studies used problem-solving therapy (PST) [21, 22, 24, 35], two used behavioural activation (BA) [34, 48] and one used psychoeducation and physical exercise [36].

Five of the studies [22, 24, 34–36] involved practitioners with mental health training, while two [21, 48] involved people with limited or no mental health training when delivering the psychological intervention. The practitioners with mental health backgrounds included nurses [22, 34, 35], psychologists [24, 34, 36], social workers [24] and occupational therapists [24]. In the two studies where health professionals with little or no mental health background carried out the intervention, community pharmacy staff [48] and lay health counsellors (LHCs) [21] (who were members of the local community with a bachelor’s degree in a non-health related field) were responsible for delivering the interventions. Other health workers involved in additional components of the interventions included physiotherapists [36] and diabetologists [36].

In the two studies involving professionals with limited or no mental health background, specific training on intervention delivery was provided. Community pharmacy staff attended a 2-day workshop training, followed by a telephone-based competency assessment in the study by Chew-Graham et al.[48]. In comparison, Dias et al. [38] recruited LHCs using an interview process, in which LHCs were asked to role-play a basic aspect of the intervention. LHCs selected via interview went on to complete a 1-week training, covering all aspects of the intervention. After training was completed, LHCs were required to undertake a competency assessment, using the therapy quality assessment scale (TQS) [38].

A description of the intervention studies and their results can be found in Table 4.

4.1. Strengths and Limitations

The strengths of this review include the broad inclusion and exclusion criteria, which allow for the comprehensive examination of the topic. Another strength is the robustness of the screening and data extraction process, which involved two researchers independently screening both titles/abstracts and full-text articles, as well as conducting data extraction. Pilot testing during the screening phase and the use of a data extraction form was also incorporated as quality assurance steps to increase the robustness of the process. However, a possible limitation of this review was the exclusion of terms such as minor depression and mild depression/anxiety, which may have led to the omission of relevant studies. While these terms could be considered part of the ’subthreshold’ category, they are sometimes described separately in the literature. The heterogeneity of the studies made it difficult to assess and compare their quality. To avoid confusion, we have solely focused on subthreshold, subclinical or subsyndromal studies for this scoping review. Last, a limitation of the scoping review methodology is that it does not involve a thorough assessment of the risk of bias or the quality of the studies. In scoping reviews, articles are not typically critically appraised [58]. However, the findings from this scoping review have informed the scope and nature of the research and lay the foundation for a future systematic review when sufficient studies are available.

4.2. Implications of the Findings for Practice and Research

Further investigation is essential to provide healthcare practitioners with clear guidelines on managing LTC patients with sDep and sAnx. While this scoping review sought to assess the feasibility of a systematic review, the current lack of evidence suggests it is premature for such an undertaking due to the limited and heterogeneous studies. More RCTs in primary care would enrich the literature and pave the way for a subsequent systematic review. Most RCTs in this review indicated potential benefits in treating LTC patients with sDep and sAnx, but high-quality RCTs are imperative to determine the true impact of these interventions.

Studies examining the role of health professionals in the screening and management of sDep and sAnx in primary care are also needed. Given the challenges in implementing mental health interventions, qualitative and codesign studies would be beneficial to develop interventions that meet the needs of consumers and health professionals. This could result in a more acceptable and effective intervention for all involved.

Based on our scoping review and prior studies, people with LTCs are more likely to experience subthreshold as well as clinical depression and anxiety [59]. We have formulated some recommendations to improve the care and management of sDep and sAnx (Table 5), which we describe further below. Screening for both depression and anxiety, rather than either condition in isolation, would be sensible given the strong overlap of the two conditions in clinical settings [60]. For example, it would be feasible to screen LTC patients annually for depression and anxiety alongside routine physical health assessments. This is a practical and reasonable timeframe to monitor any changes in the mental health of LTC patients.

Balancing brevity, reliability and validity, the PHQ-9 and GAD-7 questionnaires would be appropriate tools for screening LTC patients with sDep and sAnx, respectively, in primary care. When using a threshold of a score of 10 or more, both tools have good specificity and sensitivity for clinical depression and GAD [61, 62]. PHQ-9 and GAD-7 scores between 0 and 4 indicate minimal to no symptoms, while scores between 5 and 9 could be used as a measure for sDep and sAnx.

Appropriate management for LTC patients with sDep and sAnx would involve delivering brief interventions in a stepped-care approach. Self-help or guided self-help low-intensity psychological interventions, such as BA and PST would be potential options for managing sDep and sAnx. Other intervention options, such as psychoeducation and general lifestyle counselling may also be appropriate. Referral to GPs or specialists is necessary when the above treatments are not sufficient or when depressive and anxiety symptoms progress to more severe presentations. A possible intervention pathway is shown in Figure 2.

Non-mental health-trained professionals have the potential to deliver brief interventions with appropriate training. Studies in this review have shown that non-mental health-trained professionals can effectively deliver brief interventions, such as BA and PST [21, 48]. Therefore, this area is suitable for a range of health professionals, as it is less complex than managing clinically diagnosed disorders. Health professionals, such as pharmacists, can significantly contribute to easing the burden on GPs and mental health services, while maximising the reach of potential mental health interventions. While there is potential for non-mental health-trained professionals to deliver interventions, further exploration is needed in this area as there are several aspects to the process, and the screening process may need assessment by a trained health professional.

The key take home messages of this review are summarised in Figure 3.