Principal finding 1: somatic symptoms of depression

Figure 2 maps the number of papers identifying different ICD-11 and non-ICD-11 features of depression in 14 papers reporting symptoms among South Asian participants (Group A). This includes ten qualitative papers examining experiences reported by participants during interviews, ^{Reference Akram21–Reference Gask, Aseem, Waquas and Waheed26,Reference Mallinson and Popay29,Reference Rafique30,Reference Yusuf32} and four quantitative papers reporting symptoms measured using questionnaires. ^{Reference Ahmed, Ahmed, Carmichael and Sami20,Reference Lai and Surood28,Reference Silveira and Ebrahim31,Reference Malik40} The cardinal symptom of low mood was reported in the greatest number of papers (12 of 14). ^{Reference Ahmed, Ahmed, Carmichael and Sami20–Reference Silveira and Ebrahim31} However, the cardinal symptom of anhedonia was reported in the same number of papers (8 of 14 ^{Reference Akram21,Reference Brijnath and Antoniades22,Reference Chalal24,Reference Fenton and Sadiq-Sangster25,Reference Lai and Surood28,Reference Rafique30,Reference Silveira and Ebrahim31,Reference Bottorff, Johnson, Venables, Grewal, Popatia and Hilton44} ) as the non-cardinal somatic symptoms of sleep disturbance (8 of 14 ^{Reference Ahmed, Ahmed, Carmichael and Sami20,Reference Burr23–Reference Fenton and Sadiq-Sangster25,Reference Grewal27,Reference Mallinson and Popay29,Reference Rafique30,Reference Yusuf32} ) and physical pain (8 of 14 ^{Reference Akram21,Reference Burr23,Reference Fenton and Sadiq-Sangster25,Reference Mallinson and Popay29–Reference Yusuf32,Reference Malik40} ), one of which (pain) is not listed in ICD-11. Reports of sleep disturbance included difficulty falling asleep, early morning awakening and disturbed sleep. Reports of pain included unspecified physical pain, body aches and pains, neck pain and headaches. Other somatic symptoms reported included nausea and vomiting, ^{Reference Burr23,Reference Gask, Aseem, Waquas and Waheed26,Reference Grewal27} sensations related to the heart, ^{Reference Akram21,Reference Burr23,Reference Fenton and Sadiq-Sangster25,Reference Silveira and Ebrahim31} temperature-related sensations, ^{Reference Fenton and Sadiq-Sangster25,Reference Mallinson and Popay29} feelings of heaviness, ^{Reference Brijnath and Antoniades22,Reference Mallinson and Popay29} feelings of numbness ^{Reference Mallinson and Popay29} and sensations of pressure, squeezing or squashing. ^{Reference Brijnath and Antoniades22,Reference Burr23,Reference Fenton and Sadiq-Sangster25,Reference Gask, Aseem, Waquas and Waheed26,Reference Mallinson and Popay29} Somatic symptoms were also reported in quotations provided in the 18 papers in Group C, in which authors did not specifically analyse depressive symptoms (in studies including Pakistani, Indian, Bangladeshi, Punjabi, Sri Lankan, Afghan, Tamil and unspecified ‘South Asian’ participants ^{Reference Agarwal-Narale41–Reference Dein46,Reference Hussain and Cochrane48,Reference Morrow and Krishna52,Reference Robinson54–Reference Upadhya57} ), with participants reporting, for example ‘terrible headache’, ^{Reference Pandalangat53} ‘felt sick’, ^{Reference Agarwal-Narale41} burning sensations ^{Reference Bottorff, Johnson, Venables, Grewal, Popatia and Hilton44} , dizziness and fainting ^{Reference Akram21,Reference Dein46,Reference Pandalangat53} and hair loss. ^{Reference Ahmad, Shik, Vanza, Cheung, George and Stewart42}

Table 1 reports the 11 papers (8 quantitative, 3 qualitative) that compared symptoms between South Asian and White participants (Group B). Only the two most recent of these reported their findings in relation to ICD or DSM ⁷ symptoms, and neither found a significant difference in somatic symptoms between South Asian and White patients. These included a 2017 qualitative study comparing Anglo-Australian and Sri Lankan depression patients living in Australia, ^{Reference Antoniades, Mazza and Brijnath33} and a 2020 quantitative study using clinical records of south London (UK) depression patients aged over 65 years. ^{Reference Mansour, Tsamakis, Rizos, Perera, Das-Munshi and Stewart19} However, earlier studies comparing South Asian and White participants included symptoms not listed in ICD and, overall, these studies indicate a possible pattern of South Asian individuals experiencing higher rates of somatic symptoms compared with White individuals. A 2007 qualitative study used semi-structured interviews and distress screening tools (Self-Reporting Questionnaire, ^{Reference Beusenberg and Orley59} Schedules for Clinical Assessment in Neuropsychiatry ^{Reference Wing, Babor, Brugha, Burke, Cooper and Giel60} and Life Events and Difficulties Schedule ^{Reference Brown and Harris61} ) to explore representations of distress among Pakistani and White people in north-west England. While the authors reported no clear difference in the prevalence of somatic symptoms overall, Pakistani participants reported temperature changes and feelings of pressure and heaviness in the head, which White patients did not. ^{Reference Mallinson and Popay29} A 1996 quantitative study compared rates of depression symptoms (measured through the Hospital Anxiety and Depression Scale (HADS) ^{Reference Zigmond and Snaith62} ) and somatic symptoms (measured through the Bradford Somatisation Index (BSI) ^{Reference Mumford, Bavington, Bhatnagar, Hussain, Mirza and Naraghi63} ) among White and Asian (predominantly Pakistani and Indian) patients at two GP practices in England. Affective and cognitive elements of depression measured using HADS were similar between groups, but Asian patients were more likely to report a ‘weak or sinking heart, ‘aches and pains all over the body’ and ‘a feeling of heat inside your body’ on BSI. ^{Reference Sham, Farooq, Gahir, Okyere, Sheikh and Oyebode39} A 2004 study measured symptoms among White English and Punjabi primary care patients in London using the General Health Questionnaire (GHQ-12) ^{Reference Goldberg64} and the Amritsar Depression Inventory (ADI), ^{Reference Singh, Verma, Verma and Kaur65} the latter having been developed in the Punjab region of India, containing somatic symptoms not included in GHQ-12. ^{Reference Bhui, Bhugra, Goldberg, Sauer and Tylee36} The researchers also conducted a second-stage interview that included questions about somatic symptoms. They found that Punjabi patients with somatic symptoms (defined as ‘any sort of ache or pain, for example headache or indigestion, or any other sort of bodily discomfort’ that the patient considers is ‘due to, or made worse by, feeling low, anxious or stressed’) were more likely to report depression than White English patients with somatic symptoms defined in the same way; ^{Reference Bhui, Bhugra, Goldberg, Sauer and Tylee36} however, another paper from the same team reported that the ADI item ‘I feel sad because of aches and pains’ was a predictor of depression cases in White English patients but not in Punjabi patients. ^{Reference Bhui, Bhugra and Goldberg34} (We suggest that the presence of physical illnesses may affect responses to this latter item, but because physical illnesses were not reported in the paper their impact cannot be assessed.) A 1997 thesis used GHQ-28 to compare symptoms of Pakistani people in Britain with both a White British sample and a sample of Pakistani people living in Pakistan. ^{Reference Malik40} GHQ-28 includes somatic symptoms such as temperature-related sensations, headaches and a feeling of pressure in the head and, when using this tool, the study found that Pakistani people living in Britain had levels of somatic symptoms similar to those living in Pakistan, which were higher than for the White British sample.

Overall, our analysis paints a picture of South Asian diaspora patients experiencing a range of somatic symptoms of depression, with sleep changes and physical pain reported in the most studies. Studies directly comparing recognised symptoms among South Asian and White participants did not find that sleep changes, or any ICD somatic symptoms, were more prevalent among South Asian participants. However, other somatic symptoms not captured in ICD, such as physical pain, sensations of pressure and heaviness, and temperature-related sensations, were found to be more prevalent among South Asian than White samples.

Principal finding 2: references to the heart

A 1996 study used BSI to measure somatic symptoms among patients of different ethnicities in south London. The authors found that South Asian (predominantly Pakistani, some Indian) patients were more likely than White patients to report ‘weak or sinking heart’ on BSI. ^{Reference Sham, Farooq, Gahir, Okyere, Sheikh and Oyebode39} This was identified as potentially being related to idiomatic use of these phrases in both Punjabi and Urdu. In Punjabi, ‘sinking heart’ refers to a condition that has both physiological and psychological aspects, which are understood to interrelate. ^{Reference Krause66} ‘The heart sinks’ is used in Urdu to express sadness and despair, while ‘weakening heart’ can be used to describe someone who is easily fearful or overwhelmed. Similar language was used in qualitative studies. In a 1996 qualitative study of South Asian (mostly Punjabi) women in the UK, participants used expressions including ‘my heart kept falling and falling’, ‘the life would go out of my heart’, ‘my heart is weak’ and ‘my heart felt as if someone was pushing it down’. ^{Reference Fenton and Sadiq-Sangster25} A 2012 qualitative study of Pakistani (85%) and Indian (15%) Muslim immigrants in Toronto, Canada, reported that Punjabi-, Hindi- and Urdu-speaking participants described heart-related experiences including ‘sinking heart’, ‘dead heart’ and ‘emptiness of heart’. ^{Reference Akram21}

It is not possible to clearly delineate between references to the heart that refer to somatic symptoms and those which do not. Indeed, there are different perspectives on whether references to the body in accounts of distress and depression should be understood as somatic, metaphorical or as expressions of a way of understanding distress that understands the body and mind as part of a single experience. A 1995 quantitative study of elderly Bengali people in London found that 77% of participants reported heart-related symptoms such as pounding and breathlessness. ^{Reference Silveira and Ebrahim31} In contrast, Akram, author of the aforementioned 2012 study of South Asian Muslims in Toronto, interpreted expressions relating to the heart as referring to affective, rather than somatic, experiences, including sadness and emotional turmoil. ^{Reference Akram21} However, quotes from participants in her thesis suggest that heart-related symptoms were, at times, experienced physically:

Some have suggested that references to the body, including the heart, in South Asian expressions of distress should be understood within the context of a non-Cartesian understanding of the relationship between mind and body. Krause argues that, for Punjabis, sinking heart ‘has at the same time a somatic and psychological meaning’. ^{Reference Krause66} Participants in several studies made reference to cognitive symptoms in relation to the heart, using phrases including ‘thinking too much in my heart’ (Punjabi participants ^{Reference Fenton and Sadiq-Sangster25} ), ‘my heart was sinking with these thoughts’ (Indian Hindi speaker ^{Reference Akram21} ) and ‘thoughts and words in my heart’ (South Asian Muslim ^{Reference Hussain and Cochrane48} ). Participants in some papers made references to causal relationships between body and mind. For example, in a 1996 study of South Asian women in the UK, participants (who were mostly Punjabi) expressed that thinking in the heart led to illness, including pressure in the head (causing headaches ^{Reference Fenton and Sadiq-Sangster25} ). In a 2015 study on mental health conceptualisations among young Nepalese people in the UK, one participant expressed the belief that ‘the worry or stress or tension keeps adding up and makes somebody have headaches or fever’. ^{Reference Upadhya57} Meanwhile, a 1997 study comparing Pakistani patients with depression in the UK with White British and Pakistani (in Pakistan) patients found that Pakistani patients living in Britain, and those living in Pakistan, understood depression through a conceptualisation of the ‘emotional body’ (a term coined by Ots in relation to Chinese medicine ^{Reference Ots67} ), rejecting the body–mind dichotomy, and this distinguished them from White UK patients. ^{Reference Malik40} These accounts appear to support a non-dualistic conceptualisation of depression symptoms, with cognitive and somatic symptoms being experienced holistically. This is consistent with the Ayurveda and Unani Tibb medical systems, which are widely practised in South Asian countries. ^{Reference Sheehan and Hussain68,Reference Obeyesekere69}

Principal finding 3: repetitive negative thinking

A 2006 cross-cultural comparison of conceptualisations of depression in the UK found that older South Asian adults were more likely to see depression as related to trouble with the mind and thinking, compared with older Black Caribbean and White British adults, who were more likely to see it as related to mood. ^{Reference Lawrence, Murray, Banerjee, Turner, Sangha and Byng51} A 2007 comparison of British Pakistani and White British patients found that Pakistani patients were more likely to refer to ‘too much thinking’. ^{Reference Mallinson and Popay29} A 2017 cross-cultural comparison of experiences of depression in Australia found that people of Sri Lankan heritage explained their depression in terms of ‘overthinking’, while Anglo-Australians did not. ^{Reference Antoniades, Mazza and Brijnath33}

Repetitive thinking was a reported symptom in five symptom analyses (Group A ^{Reference Fenton and Sadiq-Sangster25,Reference Gask, Aseem, Waquas and Waheed26,Reference Mallinson and Popay29,Reference Rafique30,Reference Yusuf32} ), and was also reported by participants in studies that did not provide an analysis of symptoms (Group C). Ways of describing this included ‘thinking negatively all the time’, ^{Reference Akram21} ‘thoughts go around in your head’, ^{Reference Lawrence, Murray, Banerjee, Turner, Sangha and Byng51} ‘thinking too much’, ^{Reference Fenton and Sadiq-Sangster25} thoughts repeating themselves ‘like a film’ ^{Reference Fenton and Sadiq-Sangster25} and ‘I repeatedly kept thinking about things’. ^{Reference Gask, Aseem, Waquas and Waheed26} These experiences sometimes included references to a sense of thoughts being uncontrollable, and/or that repetitive thinking was having a detrimental impact on health. ^{Reference Rafique30,Reference Upadhya57} Repetitive negative thinking is not listed as a symptom of depression in ICD-11. One form of repetitive negative thinking is rumination, ^{Reference McEvoy, Mahoney and Moulds70} which has been found to be more common in depression where trauma is a factor, than in depression without trauma. ^{Reference Birrer and Michael71,Reference Cano-López, García-Sancho, Fernández-Castilla and Salguero72} Some studies reported depression symptoms as responses to trauma among Punjabi, Afghan, Tamil and Indian participants. ^{Reference Chalal24,Reference Agarwal-Narale41,Reference Johnson50,Reference Morrow and Krishna52,Reference Pandalangat53} Meanwhile, trauma is known to be a common aspect of experience among migrant populations, ^{Reference Tummala-Narra73,Reference Lijtmaer74} and it has been argued that mental health among the South Asian diaspora is impacted by intergenerational trauma. ^{Reference Qureshi, Misra and Poshni75} It is possible that the prevalence of repetitive negative thinking among the South Asian diaspora may be related to trauma among this population.

Gap identified: acculturation and ethnic differences

Only four papers considered acculturation differences in their analyses of depression symptoms, ^{Reference Lai and Surood28,Reference Bhui, Bhugra and Goldberg34,Reference Bhui, Bhugra, Goldberg, Sauer and Tylee36,Reference Malik40} and each of these is at least 17 years old. A 2000 study assessed the validity of GHQ-12 and ADI (developed in the Punjab region of India) among Punjabi and White English primary care patients in south London. ^{Reference Bhui, Bhugra and Goldberg34} The team found that ADI was better at detecting depression among White English patients than Punjabi patients, but that it was not a valid tool for use with either group. Among Punjabi patients who had been in England for more than 30 years, ADI was no better than chance. GHQ-12 was a more valid tool for measuring depression in both Punjabi and White English patients, and its validity among Punjabi patients did not change depending on length of residency in England, which suggests that there were no acculturation differences in the validity of GHQ-12. The article did not include analysis of acculturation differences in specific symptoms. A 2008 study of older South Asian Canadians (majority Indian) used the Geriatric Depression Scale (GDS) and found that length of residency was not significantly associated with depression caseness, but that those who had been in Canada for <10 years were more likely to report ‘feeling not in good spirits most of the time’ and ‘not feeling happy most of the time’ than those who had been in Canada >10 years. ^{Reference Lai and Surood28} It should be noted, however, that GDS includes only one somatic symptom – psychomotor agitation. This means that none of the somatic symptoms most prevalent in South Asian countries ^{Reference Haroz, Ritchey, Bass, Kohrt, Augustinavicius and Michalopoulos5} were assessed. Two further studies found no acculturation differences. ^{Reference Bhui, Bhugra, Goldberg, Sauer and Tylee36,Reference Malik40} Overall, no acculturation pattern can be discerned from these four studies. There was a lack of literature on the specific experience of people of South Asian heritage born in English-speaking countries, and no papers compared this population with first-generation South Asian migrants.

No papers included in this review considered differences between people of different South Asian ethnicities. One study considered religious differences and found that Muslims reported ‘often get bored’ and ‘feel pretty worthless’ more often than Hindus and Sikhs, while there was no significant difference in overall depression prevalence between these groups. ^{Reference Lai and Surood28} Overall, there was insufficient evidence to draw conclusions regarding the effects of acculturation or ethnic differences in depression symptomology. This indicates a gap in research.