An observational cross-sectional study was designed after obtaining permission from the Institutional Ethics Committee. The sample size was estimated to be 350 subjects and the study was conducted during the period August-September 2014. The subjects were chosen from those attending the tertiary care unit- Pradyumna Bal Memorial Hospital, Bhubaneswar, Odisha. Written informed consent was taken from all the subjects volunteering for the study. Five different categories of patients were considered- postoperative (surgical patients undergoing various procedures except cardiac surgery and intracranial neurosurgery) post-labour, post-caesarean section, dental pain (caries, tooth extraction, dental surgery or any dental treatment with or without anaesthesia) and a control group. The control group consisted of subjects with minor illness without any pain such as psychiatric illness, skin disorders, etc. The subjects were considered for the study within 72 hours of surgery or delivery.

The subjects with history of steroids, anti-anxiety, anti-depressants, mood altering drugs and any other drug intake were excluded from the study. Persons receiving psychiatric treatment or who have been diagnosed as cases of depression previously were also excluded from the study. The subjects should not have been given any dose of analgesics prior to the study. The duration of pain was also documented. Measurement of pain was done by the subjects themselves by answering simple questionnaires such as Box scale, Visual Analogue Scale (VAS), Numeric Rating Scale (NRS), Verbal Rating Scale (VRS), Behavioural Rating Scale (BRS) [15]. These scales are freely available for assessment of pain perception. Each subject was guided step wise while filling the questionnaires and the response was cross-evaluated. Depression was estimated using the Montgomery–Åsberg Depression Rating Scale (MADRS) [16]. The subjects were categoried as normal/asymptomatic if MADRS score was 0-6. Similarly, the subjects were classified as mild depression with a score of 7-19, moderate depression with a score of 20-34 and severe depression if score is >34 [17]. All data were statistically analysed using SPSS Software version 16 (Chicago, Inc., IL, USA). Correlation coefficients were determined and a two-tailed p-value <0.05 was considered statistically significant.

A total number of 350 subjects were included in the study with 70 subjects in each of the 4 categories of patients (postoperative, post- labour, post-caesarean, dental pain) and control group. All data were expressed as mean ±SD (standard deviation) and tested for normality. The mean characteristics of all the subjects are shown in [Table/Fig-1].

Females felt pain less as compared to males; however, they seemed to be more depressed than males as shown in [Table/Fig-2]. On applying one-way ANOVA test to the different age categories we can report that the geriatric population suffered most from depression as shown in [Table/Fig-3].

Among the four groups of cases, the postoperative subjects were most depressed and perceived more pain as compared to other groups. This can be depicted by [Table/Fig-4] and [Table/Fig-5]. The association between the depression (measured via MADRS score) and the various pain scales are shown in [Table/Fig-6].

[Table/Fig-4]:

Depression compared in the different categories of cases

*p<0.0001 (highly statistically significant) on applying one-way ANOVA between the groups

The Box scale of pain measurement is considered the simplest and often used method of pain assessment. In this method, most of the cases reported a pain scale of 6 (25.4%) followed by scale of 5 (23.6%), scale of 4 (18.2%) and scale of 3 (16.1%). The extremes of the scale were represented by 0.7% of total subjects.

On categorizing the subjects based on MADRS depression scores into mild, moderate and severe depression levels, it was evident that pain was increased with respect to increasing depression as shown in [Table/Fig-7].

Plotting a graph between the duration of pain and the level of depression, it is seen that at about 24 hours and at about 48 hours after start of pain, the depression levels are at a peak (shown in [Table/Fig-8]).

[Table/Fig-8]:

MADRS scores plotted against duration of pain (in hours)

A total of 280 subjects were recruited for the present cross-sectional study to find the association between acute pain and depression in four different and most common causes of acute pain. Dental pain is a very common cause of acute pain which is at times unbearable. The psychosomatic impact of the various conditions was assessed using an easily comprehensible, self-rating, highly senstive Montgomery–Åsberg Depression Rating Scale (MADRS) which is commonly employed by psychiatrists to measure the severity of depressive episodes in patients with mood disorders. Various scales of acute pain measurements were used, as any single scale might not be an accurate predictor of degree of pain. The subjects were chosen from those attending a tertiary care unit to focus on the upper and middle class socio-economic people. Since depression is more prevalent in the upper strata of socio-economic class [18], this subset of population was included in this study.

Subjects with a wide range of age groups were incorporated in the study so as to see if there are any changes in pain perception and depression levels with increasing age. It was seen that the geriatric population were more depressed than the other age groups [19]. However, the older adult’s population (45-60 years) perceived more pain. Poor self-rated health is more often viewed as a concomitant phenomenon of depression rather than an independent risk factor for increased depression. There are several reasons to expect that age plays a role in the relationship between pain and depression. Older people tolerate pain more than the younger population and also it has been hypothesized that with advancing age the “experience of pain” does not change but the “experience of discomfort” becomes normative [19].

The subjects were assessed for depression and acute pain in the first 72 hours of surgery or onset of pain. This was considered pivotal for the study to see the levels of depression during the initial period of pain, without any medicinal management. A control group of 70 subjects without any painful conditions and without any depressive illness were compared with the cases to prove the fact that acute pain and depression are co-morbid states and the onset is also simultaneous. No underlying depression was seen in the control group as expected.

Gender difference to pain perception was quite evident by the fact that females reported less pain than males. It is believed that women may have different pain beliefs and may experience depression as a more socially acceptable reaction to pain than males do [19]. The female population was more in this study due to inclusion of post-labour and post-CS patients. The females have accepted the belief that they have higher rates of pain endurance during child-birth, irrespective of the parity. Thus, these categories of subjects showed much lesser perception of pain as compared to other categories of subjects. But, the degree of depression occurring in females is an alarming issue as many women tend to suppress their depression leading to mortality due to suicides [20]. A contributing factor might be the lack of attention to the mental status of women, especially in Eastern Odisha, where they are more or less neglected.

Acute pain score was highest reported in postoperative patients followed by dental pain, post-CS and post-labour. Onset of pain prior to the surgery, which gets aggravated by anaesthesia and blood loss during the surgery, may be contributing factors for the increased perception of acute pain. This pain is more profound after 24 hours and 48 hours of surgery, after which it shows a gradually decreasing trend. Dental pain which is often ignored by medical practitioners is another common cause of acute pain, but it does not contribute to moderate or severe depression. The patient assumes that dental pain is a very short-term acute pain and would be relieved sooner with medications or attention. This might be a possible explanation. Post-CS acute pain causes more depression than the post-labour pain due to surgical intervention in case of caesarean section.

Acute pain is always known to be associated with some behavioural changes and psychotic effects. Thus the VRS scale has the strongest association with depression scores by MADRS, followed by other pain scales. With increasing pain scale, there is no strong linear relationship with depression, opposite to the fact that with increasing levels of depression, the acute pain perception is also decreased. However, some studies have shown controversial results, stating that pain and depression share a linear relationship with each other [11]. This might be the result of the previous studies considering both acute and chronic pain while our study incorporates only cases of acute pain.

This study is unique as, in India, especially in eastern Odisha region, there has been no documented literature regarding pain and depression co-morbidity states. Moreover, many previous works have been done on chronic pain and its relationship with depression. However, very scanty literature could be collected on acute pain and its association with depression. Wide range of age groups, different categories of causes of acute pain, usage of more than one form of pain scale adds to the strength of this study.

However, this study has its limitations, one of which is the fact that the subjects might have underlying depression even before the onset of painful morbidity state, and it would have been aggravated by the acute pain condition. A prospective study could be taken up to follow-up the subjects beyond the 72 hours period to assess the pattern of depression with respect to pain management by medication and other non-medical ways. Also, the effect of analgesics on depressive states can be studied in future follow-up studies.

To conclude, acute pain and depression co-exists and forms an alarming issue which needs urgent addressable attention by our health care practitioners. Palliative care and pain management clinics need to be established in more numbers and psychosomatic approach to treatment should be incorporated while treating any disease condition presenting with acute pain. Also, the psychosomatic component of pain physiology needs to be studied in further details.