Association of depression and chronic lower-back pain

Method: One hundred consecutive patients visiting an orthopaedic out patients department (OPD) with chronic lower – back pain in a tertiary hospital were included. They were interviewed for major depressive disorder (MDD) using DSM-5 and assessed for the severity of depression, health-related quality of life and sleep quality using the Hamilton Depression Rating Scale, Health Questionnaire Short Form (SF-36) and Pittsburgh Sleep Quality Index (PSQI), respectively. Proportion was compared using chi-square test, scores of scales were compared using the Mann – Whitney test and Kruskal-Wallis test followed by Dunn’s post-hoc multiple comparisons. Statistical data were analyzed by Graph Pad InStat version 3.06.A p value of <0.05 was considered statistically significant.


INTRODUCTION
Pain is an unpleasant sensory and emotional experience that is always subjective [1].Backache is the most commonly reported type of pain, followed by headache then knee pain [2].It is defined as pain and discomfort, localized below the costal margin and above the inferior gluteal folds [2].It is one of the most common causes of seeking physician visits, and because of high direct and indirect costs it has great medical ,social and economic impact for the individual, their family and society at large [2] the pain can be localized in upper, middle or lower(back).Low back pain is a common health problem worldwide and a major cause of disability, affecting performance at work and general well-being [2].Low back pain is classified on the basis of its duration as acute (<6 weeks), sub-acute (6-12 weeks) and chronic(>12 weeks) [4].
Psychological factors are important in people with chronic low back pain.Research has indicated that depression and chronic low back pain could be interrelated [5][6][7][8][9].Major depressive disorder is a mood disorder that is characterized by depressed mood for most of the day ,nearly every day, as indicated either by a subjective report or by observation and/or loss of interest in a previously pleasurable activity, that have been present during the same 2 week period, but there might be other symptoms as well [10].
Both conditions are frequently observed in the general population and have high morbidity rates.Up to 30% of individuals, who report low back pain, have recurrent or persistent symptoms [11].As a result, chronic low back pain is one of the most common reasons for medical visits.Studies have reported that 55% of chronic low back pain (CLBP) patients experienced sleep disturbance after pain onset [12,13].To the best of our knowledge there is paucity of data, on the prevalence of depression in patients suffering from chronic lower -back pain.This study was conducted to assess the frequency of major depressive disorder, quality of sleep, permanent functional disability and the association of MDD with the above mentioned variables in a tertiary care setting.

Subjects
One hundred consecutive patients visiting orthopedic outpatient department in a tertiary care hospital during October 2015 to march 2016 were included in the study.Patients were of both genders, aged more than 30 years and had lower -back pain as a primary complaint, for a period of more than 12 weeks.Pregnant and lactating females along with severely ill, bedridden patients those with a history of psychiatric illness ,patients suffering from severe mental illnesses including schizophrenia, bipolar mood disorder, cognitive impairment, chronic disabling illnesses, negative symptoms, dementia, and poor attention as well as those unable to give verbal replies were excluded from the study.
Patients were interviewed by the principal investigator on various demographic variables such as age, gender, religion, residence, education, socioeconomic status, height, weight and body mass index, treatment for lower back pain, its duration and mode, and the duration of backache.Personal and family history of any psychiatric illness was recorded as well.
All patients were interviewed for a diagnosis of major depressive disorder (MDD) using DSM-5 [2] criteria.The diagnosis was confirmed by a consultant psychiatrist with more than 25 years of experience in the subject.Every patient was assessed for the severity of depressive symptoms, health-related quality of life, sleep quality, lower-back pain severity and permanent functional disability on the Hamilton Depression Rating Scale [14,15] which is a 17item observer-rated scale for assessing the severity of depression; and by the Short Form 36 Health questionnaire [16] that is a multi-purpose short-form health survey with 36 questions.It yields an 8-scale profile of functional health and well-being scores as well as psychometrically based physical and mental health summary measures and a preferencebased health utility index.They were also assessed with the Pittsburgh Sleep Quality Index (PSQI) [17], a self-rated sleep quality questionnaire and by the Oswestry Low Back Disability Questionnaire [18], which is an important tool that researchers and disability evaluators use to measure permanent functional disability in a patient.
Qualitative data were expressed as percentages and quantitative data as median ± interquartile range.Statistical analysis was performed using Graph Pad in Stat version 3.06 (San Diego, California, US).The proportion of participants was compared by using chi-square test the while scores on HAM D,SF 36,PQSI and Oswestry index were compared using the Mann-Whitney Utest and Kruskal-Wallis test followed by Dunn's post-hoc multiple comparisons.The Statistical correlation between the severity of depressive symptoms and permanent functional disability due to back pain were assessed by Spearman's rank correlation.
A p value of <0.05 was considered statistically significant.
Written informed consent was obtained from every patient.Prior approval for the study had been obtained from the local ethics committee.

AIMS AND OBJECTIVES
To study the frequency of major depressive disorder, assess sleep quality, permanent functional disability; association of major depressive disor-der with permanent functional disability; quality of life and quality of sleep in patients with chronic lower-back pain; also to study the correlation between permanent functional disability due to lower-back pain and the severity of depressive symptoms.

RESULTS
On recruiting 100 consecutive patients we assessed their socio-demographic and other historical characteristics (Table1).Data were presented as No.(%) .In the present study 36(%) were males and 64 (%) were females among 100 patients.The mean age of the patients was 51.02 +/-13.5 years, mean duration of backache was 31.12 months.Data were presented as No.(%).Diagnosis of major depressive disorder was made by clinical interview as per the DSM-5 criteria [2].Data were represented in numbers (%) or mean ± S.D, groups were compared by Chisquare test & Mann Whitney U test, p<0.05 is considered to be statistically significant.Patients with chronic lower-back pain were grouped;(1) With MDD and (2) without MDD as shown in Table 3.
We divided the patients into groups with and without MDD.Patients with chronic lowerback pain with MDD scored significantly higher(0.048)on Oswestry low backache disability questionnaire as compared to patients without MDD, which suggests that patients with MDD had higher permanent functional disability than patients without MDD.Similarly, patients with MDD scored significantly higher on the Pittsburgh Sleep Quality Index (<0.0001) and on, HAM D (<0.0001).There were statistically significant differences in the all domains of the quality of life, except social functioning, which suggests that patients with MDD had lower quality of life as compared with patients without MDD.Data are represented as mean ± S.D ,groups were compared using a Chi Square test and, Mann Whitney U test, p<0.05 is considered to be statistically significant -HAM D Hamilton depression rating scale, SF 36 short form 36.
Participants were divided in two groups on the basis of duration of lower-back pain: (1) with 1 year or less (n=59), (2) and more than 1 year (n=41).Significant difference was observed in both groups on depression (p=0.008).No statistically significant difference was observed in both groups on HAM-D score(p=0.25),Oswestry lower-back pain disability questionnaire score(p=0.052),PSQI score(p=0.06)andall domains of SF 36 score as shown in Table    Data are shown in mean ± S.D.All the groups were compared by Kruskal-Wallis test followed by Dunn's post-hoc multiple comparisons.† P< 0.05 in comparison with other groups.We divided the patients into three groups: (1) With mild permanent functional disability due to lower-back pain; (2) with moderate permanent functional disability due to lower-back pain; (3) severe and very severe permanent functional disability due to lower-back pain lowerback pain, as shown in Table 6.Data is represented in Mean ± S.D ,groups were compared by Chi Square test ,Mann Whitney U test, p<0.05 is considered to be statistically significant, HAM D Hamilton depression rating scale, SF 36 short form 36.
Participants were divided in two groups: ((1) with treatment received (n=53), and( 2)with no treatment (n=47).A significant difference was observed in both groups on severity of depression (HAM D score) (p=0.0067), and physical health (0.0148).No significant statistical difference was observed in both groups on depression (p=0.205),Oswestry low backache disability questionnaire score (p=0.94),PSQIscore (p=0.716) and all domains of SF 36 as shown in Table7.

DISCUSSION
It was observed in the present study that 74 patients with chronic lower-back pain who vis-ited orthopedic, out-patients department suffered from MDD on the basis of DSM-5 diagnostic criteria.Many previous studies have shown depression to be prevalent among people with chronic back pain [4,5,7,16,19,20].In clinical samples of previous studies rates of major depression in such patients ranged from 30% to 62.8 %, which is significantly higher than the rate found in the general population [21,22].
Out of 100 patients recruited to the study, 81 had significantly poor sleep quality.This is consistent with other studies :Graine et al. [23] recorded a frequency of 86.6%on the basis of Pittsburgh Sleep Quality Index, and Morin et al. [24] and Gráinne et al. [25] have also found high prevalence of poor quality of sleep in patients with lower-back pain.
It must be noted that comparing these studies was a difficult task because of differences in study populations, applied tools, cut-off points and differences in social and cultural contexts.
The present study noted that there was no significant difference in the frequency of depression with demographic variables;, similar results were noted in other studies [10,26].In a study conducted on the Korean population patients with chronic lower-back pain with depression had a poorer quality of life compared with those who did not have depression, which is consistent with the results of our study.Other studies reported similar findings [10,27].
We observed that patients with chronic lowerback pain with depression had higher functional disability than patients who did not suffer from depression, similar to other studies [28,29] (Table 6).It has also been found that depression in patients with chronic lower-back pain is associated with poorer quality of sleep [13,29].
We observed that patients who had lower-back pain for more than 1 year had higher frequency of depression than patients who had pain for lesser than 1 year, which is consistent with the results noted in a study conducted by Kimney et al. [30], but inconsistent with a study conducted by Michael et al. [6].
A strong correlation (Spearman r =0.5220, P<0.0001)was established between functional disability and severity of depressive symptoms(see Figure 1) .The correlation between disability and depression has been well demonstrated by previous studies [7,8] which showed positive but weak correlation.It should be noted that it is difficult to establish the cause and effect relationship on the basis of correlation.Depression itself is a debilitating condition and disability caused due to lower-back pain may in itself lead to depression, which further increases the disability.
Similar to other studies [6,7], patients with severe functional disability had poorer quality of sleep, severe depressive symptoms, poorer quality of life in all domains except role limitations due to physical health, less energy and greater fatigue, worse emotional well-being and greater pain.
It was also observed that patients who were on treatment for backache had severe depression and poorer quality of life in role limitations due to physical health compared with patients who were not on any treatment, which can be due to multiple reasons such as severity of ill-ness, cost of treatment, accessibility and availability of treatment.Similar results were found in a study conducted by Ritzwoller et al. [31].
This study has several limitations -it was a single-centered study, with small sample size.Participants were recruited from a tertiary care hospital and they do not represent the general population.A further larger-scale randomized study is needed.A longitudinal study is required to study the cause effect relationship of depression and lower-back pain. .

Figure 1 .
Figure 1.Correlation of severity of functional disability due to lower-back pain with severity of depression

Table 1 .
Socio-demographic characteristic and other factors related to patients with chronic lower-back pain

Table 2 .
Frequency of major depressive disorder and poor quality of sleep in patients with chronic lower-back pain according to DSM-5 criteria and on the basis of PQSI scores(global score >5) respectively

Table 3 .
Demographic variables according to the presence or absence of major depressive disorder

Table 4 .
Association of major depressive disorder with severity of depressive symptoms (HAM D), Oswestry low backache functional disability score, quality of sleep (PSQI) and quality of life (SF 36) in patients with chronic lower-back pain

Table 5 .
Association of duration of lower-back pain with depression, severity of depressive symptoms (HAM D), Oswestry low backache functional disability score, quality of sleep (PSQI) and quality of life (SF 36 score ).

Table 6 .
Association of lower back pain functional disability with major depressive disorder, severity of depressive symptoms (HAM D), quality of sleep(PSQI) and, quality of life (SF 36 score ) in patients with chronic lower back pain

Table 7 .
Association of treatment with major depressive disorder lower-back pain, severity of depressive symptoms(HAM D), functional disability due to lower-back pain, quality of sleep (PSQI) and, quality of life (SF 36 score ).