Psychiatric morbidity in patients with idiopathic Parkinson's disease: A cross-sectional study.

OBJECTIVE: To evaluate the prevalence of psychiatric comorbidities in patients with idiopathic Parkinson's disease (IPD).
METHODOLOGY: Two hundred and thirty-nine patients with IPD were evaluated on Mini-International Neuropsychiatric Interview PLUS (MINI-PLUS). In addition, patients found to have depression as per the MINI-PLUS were evaluated on Beck Depression Inventory.
RESULTS: One hundred and thirty-five (56.5%) patients had a current psychiatric diagnosis and 59.8% had a lifetime psychiatric diagnosis. As per MINI-PLUS, about two-fifth (39.7%) of patients had suicidality. In 18.8% of patients, suicidality was present in the absence of axis-I psychiatric diagnosis. Among the various psychiatric disorders, the most common disorders included depressive disorders (current: 17.5%; lifetime: 23.8%), anxiety disorders (current: 17.5%; lifetime: 17.5%), and psychotic disorders (current: 11.3%; lifetime: 11.7%).
CONCLUSIONS: More than half of the patients with Parkinson's disease have psychiatric disorders. High prevalence of psychiatric morbidity calls for close liaison between the neurologist and the psychiatric disorders. Copyright:

Psychiatric comorbidities or neuropsychiatric symptoms are quite frequently reported in patients with Parkinson's disease. The neuropsychiatric syndromes increase the disability, health service utilization, and the risk for hospitalization and decrease the overall quality of life of patients with PD.[1] The commonly reported neuropsychiatric symptoms include depression, anxiety disorders, psychosis, dementia, sleep disorders, and impulse control disorders.[2] The neuropsychiatric syndrome can be due to common etiopathogenesis as that of PD, medications used for management of PD, or as a reaction to the physical illness and its consequences. In most cases, it is more often than not multifactorial in origin.[3] Many studies across the globe have evaluated psychiatric morbidity in patients with PD. Most of these studies have either evaluated only 1 psychiatric disorder, with limited number of studies focusing on the whole range of psychiatric morbidities. Further, most of these studies have relied on the use of screening instruments to report the prevalence of various psychiatric disorders in patients with PD. The available studies have mainly focused on reporting the prevalence and incidence of depression, whereas the data for other disorders are limited. Studies which have evaluated psychosis have in general considered the time frame of last 1 week to last 6 months. Further, these studies have concentrated just on the evaluation of hallucination or have evaluated other psychotic symptoms also along with hallucinations.[2]

Few studies have focused on suicidal behavior in patients with PD, and the prevalence of suicidal ideations/death in patients with PD varies from 22.7% to 30%.[2] Only a limited number of studies are based on the evaluation of patients using various structured interview schedules such as composite international diagnostic interview and structured clinical interview for DSM-IIIR or have used DSM-IV criteria to evaluate the prevalence of depressive disorders.[2]

Very few studies from India have evaluated the prevalence of neuropsychiatric symptoms in patients with PD.[34567] Most of these studies have not relied upon the use of structured diagnostic instrument. In this background, this study aimed to evaluate the prevalence of psychiatric comorbidities in patients with idiopathic PD.

METHODOLOGY

This cross-sectional study was conducted in the outpatient setting of the department of neurology, of a tertiary care hospital. All the participants were recruited after obtaining written informed consent. Ethics committee of the institute in which the study was conducted approved the study.

The inclusion criteria for the study were diagnosis of idiopathic Parkinson's disease (IPD) as per the Ward and Gibb criteria[8] and age between 35 and 80 years. Patients with intellectual disability, head injury, comorbid serious physical illness, patients severely ill to cooperate with the interview, and patients with symptoms of Parkinsonism due to medications and other neurological and physical illnesses were excluded. The data intake for the study was done during July 2015 to June 2016.

All the patients with clinical diagnosis of IPD, attending the outpatient services (preferably drug naïve-had not received any antiparkinsonian medication), were approached. Consenting patients were assessed on the Ward and Gibb criteria[8] to confirm the diagnosis. The participants were assessed on the Unified Parkinson's Disease Rating Scale (UPDRS)[9] and Hoehn and Yahr (H and Y)[10] staging for PD to rate the severity of the PD. Mini-International Neuropsychiatric Interview PLUS (MINI-PLUS)[11] was used to evaluate the patients for the presence of psychiatric comorbidity. Those patients diagnosed to have depression as per the MINI-PLUS were further assessed for severity of depression using Beck Depression Inventory (BKI) II.[12] Those patients found to have psychiatric morbidity were offered treatment.

The data were analyzed using Statistical Package for Social Sciences, sixteenth edition (SPSS-16; SPSS Inc. Released 2007. SPSS for Windows, Version 16.0. Chicago, SPSS Inc.). Continuous variables were described as mean, standard deviation (SD), and range. Categorical variables were described as frequency and percentages. Comparisons were conducted using Chi-square test and t-test.

RESULTS

The study included 239 patients with IPD. The mean age of the study sample was 59.4 (SD-7.6) years with 30.1% patients aged 65 years or more. The mean number of years of education was 11.1 (SD-2.9) years with nearly equal representation of those educated beyond matric or those educated less than or equal to matric. Males (60%) outnumbered females (40%). Majority of the participants were married (88%) and not on paid employment (63.6%).

The mean age of onset of PD in the study sample was found to be 54.7 (SD-8.2) years, and the mean duration of PD was 63.3 (SD-50) months. Other clinical details are given in Table 1.

Table 1

Clinical profile of Parkinson’s disease (n=239)

Variable	Mean (SD) [range]/Frequency (%)
Age of onset of Parkinson’s disease	54.7 (8.2) [35-75]
Duration of Parkinson’s disease (months)	63.3 (50) [2-280]
Family history of Parkinson’s disease
Yes	28 (11.7)
No	211 (88.3)
Drug naïve (i.e., had not received any antiparkinsonian medication)
Yes	28 (11.7)
No	211 (88.3)
Both Syndopa Plus and Syndopa	94 (39.3)
Syndopa Plus	70 (29.3)
Syndopa	47 (19.7)
Pramipexole	82 (34.3)
Patients on trihexyphenidyl	43 (18.0)
UPDRS
UPDRS - mentation, behavior, and mood	7.5 (2.7) [2-13]
UPDRS - activities of daily living	23.7 (7.8) [5-40]
UPDRS - motor examination	25.8 (8.0) [9-44]
Total score in UPDRS (I+II+III)	57.1 (17.3) [21-93]
UPDRS - complications of therapy (past week)
Dyskinesia	5.5 (2.2) [0-11]
Early morning dystonia
Yes	16 (6.7)
No	223 (93.3)
UPDRS - clinical fluctuations
Are “off” periods predictable?
Yes	131 (54.8)
No	108 (45.2)
UPDRS - clinical fluctuations
Are “off” periods unpredictable?
Yes	108 (45.2)
No	131 (54.8)
UPDRS - clinical fluctuations
Do “off” periods come on suddenly within a few seconds?
Yes	131 (54.8)
No	108 (45.2)
UPDRS - clinical fluctuations (%) day
For what proportion of the waking day is the patient “off” on average?
1-25	54 (22.6)
26-50y	129 (54.0)
51-75	56 (23.4)
Other complications - GI symptoms
Yes	123 (51.5)
No	116 (48.5)
Other complications - sleep disturbances
Yes	239 (100)
No	0
Other complications - symptomatic orthostasis
Yes	142 (59.4)
No	97 (40.6)
UPDRS - Modified Hoehn and Yahr staging
Unilateral plus axial involvement (Stage 1.5)	28 (11.7)
Bilateral disease, without impairment of balance (Stage 2)	21 (8.8)
Mild bilateral disease, with recovery on pull test (Stage 2.5)	136 (56.9)
Mild to moderate bilateral disease; some postural instability; physically independent (Stage 3)	29 (12.1)
Severe disability; still able to walk or stand unassisted (Stage 4)	25 (10.5)
UPDRS - Schwab and England Activities of Daily Living (percentage)	52.2 (7.9) (40-70)
Physical comorbidity
Hypertension$	73 (30.5)
Diabetes mellitus$	29 (12.1)
Other comorbid illness£	13 (5.4)

$11 patients had both diabetes mellitus and hypertension, £4 patients had osteoarthritis and 9 patients had rheumatoid arthritis. UPDRS – United Parkinson’s Disease Rating Scale; GI – Gastrointestinal; SD – Standard deviation

Psychiatric morbidity

Out of the 239 patients, 135 (56.5%) patients had a current psychiatric diagnosis and 59.8% had a lifetime psychiatric diagnosis as per MINI-PLUS [Table 2]. As per MINI-PLUS, about two-fifth (39.7%) of patients had suicidality. In 18.8% of patients, suicidality was present in the absence of axis-I psychiatric diagnosis [Table 2].

Table 2

Psychiatric illness as assessed on Mini-International Neuropsychiatric Interview Plus (n=239)

Variable	Current diagnosis, n (%)	Lifetime diagnosis, n (%)
Total number of patients with psychiatric diagnosis other than drug dependence	111 (46.4)	127 (53.1)
Total number of patients with drug dependence	32 (13.4)	32 (13.4)
Total number of patients with a psychiatric diagnosis including drug dependence	135 (56.5)	143 (59.8)
Total number of patients with more than one diagnosis of Psychiatric illness (including drug dependence)	35 (14.6)	50 (20.9)
Psychiatric diagnosis
Major depressive disorder	23 (9.6)	38 (15.9)
Dysthymia	19 (7.9)	19 (7.9)
Manic (hypomanic) episode	1 (0.4)	1 (0.4)
Panic disorder	21 (8.8)	21 (8.8)
Agoraphobia	7 (2.9)	7 (2.9)
Obsessive - compulsive disorder	6 (2.5)	6 (2.5)
Generalized anxiety disorder	8 (3.3)	8 (3.3)
Psychotic disorders	27 (11.3)	28 (11.7)
Suicidality	95 (39.7)
Mild	64 (26.8)
Moderate	23 (9.6)
Severe	8 (3.3)
Suicidality
With axis-I psychiatric diagnosis	50 (20.9)
Without axis-I psychiatric diagnosis	45 (18.8)

The mean BDI score for patients with major depressive disorder was 45.9 (SD-5.2), with almost all patients (22 out of 23) having BDI score in the range of severe depression (total score: 29–63). The mean BDI score for patients with dysthymia was 27.0 (SD-1.6), with again almost all of such patients (18 out of 19) having BDI score in the range of moderate depression (total score: 20–28).

When the association of onset of psychiatric disorders and onset of PD was evaluated, in 62 patients (about half, i.e., 48.8% of the patients with lifetime axis-I psychiatric diagnosis other than tobacco dependence), psychiatric symptoms preceded the onset of PD. In more than one-fourth (29.1%), symptoms of PD preceded the onset of psychiatric disorder, and in 22% of patients, both the disorders started almost together.

The mean age of onset of psychiatric illness was 24.8 (SD-25.7) years and the mean duration of treatment for IPD at the time of assessment was 48.9 (SD-105.2) weeks. Family history of mental illness was seen 14.2% of cases.

Relationship of psychiatric morbidity with other variables

Those with current and lifetime axis-I psychiatric disorder were compared with those without current and lifetime axis-I psychiatric disorder, respectively, to study the factors associated with development of psychiatric disorders in patients with PD; significant differences were noted for certain demographic and clinical factors [Tables 3 and 4].

Table 3

Comparison of demographic and clinical profile of those without (Group I) and with (Group II) current psychiatric illness

Variable	Mean (SD)/Group I (n=128), n (%)	Mean (SD)/Group II (n=111), n (%)	T/χ2 (P)
Age of onset of Parkinson’s disease	57.1 (7.8)	52.7 (8.0)	−4.3 (<0.001)***
Duration of Parkinson’s disease (months)	47.4 (51.7)	77.2 (44.2)	4.8 (<0.001)***
Both Syndopa plus and Syndopa	62 (48.4)	32 (28.8)	9.6 (0.002)**
Syndopa	83 (64.8)	58 (52.3)	3.9 (0.048)*
UPDRS
UPDRS - mentation, behavior, and mood	5.9 (2.1)	9.4 (1.9)	−13.7 (<0.001)***
UPDRS - activities of daily living	18.5 (5.6)	29.8 (5.4)	−15.8 (<0.001)***
UPDRS - motor examination	20.3 (5.3)	32.2 (5.5)	−17.0 (<0.001)***
Total score in UPDRS (I+II+III)	44.6 (10.9)	71.4 (11.2)	−18.6 (<0.001)***
UPDRS - complications of therapy (past week)
Dyskinesia (%) days
<50	115 (89.8)	59 (53.2)	40.4 (<0.001)***
>50	13 (10.2)	52 (46.8)
Disability due to dyskinesia
No to moderate	108 (84.4)	65 (58.6)	19.8 (<0.001)***
Severe to complete	20 (15.6)	46 (41.4)
Painful dyskinesia
No to moderate	102 (79.7)	65 (58.6)	12.6 (<0.001)***
Severe to marked	26 (20.3)	46 (41.4)
Early morning dystonia# - Yes	0	95 (85.6)	17.5 (<0.0010***
UPDRS - Clinical fluctuations	85 (66.4)	46 (41.4)	15.0 (<0.001)***
Are “off” periods predictable? - Yes
UPDRS - clinical fluctuations
For what proportion of the waking day is the patient “off” on average? (%) days
<50	87 (68.0)	96 (86.5)	11.4 (0.001)**
51-75	41 (32.0)	15 (13.5)
Other complications: GI symptoms - Yes	40 (31.3)	83 (74.8)	45.1 (<0.001)***
Other complications: Sleep disturbances - Yes	128 (100)	111 (100)	1.00
Other complications: Symptomatic orthostasis - Yes	52 (40.6)	90 (81.1)	40.4 (<0.001)***
UPDRS - modified Hoehn and Yahr staging
<Stage 2.5	127 (99.2)	58 (52.3)	72.3 (<0.001)***
>Stage 2.5	1 (0.8)	53 (47.7)
UPDRS - Schwab and England Activities of Daily Living (percentage)	55.9 (8.2)	47.9 (4.7)	9.0 (<0.001)***
Physical comorbidity
Diabetes mellitus	10 (7.8)	19 (17.1)	4.8 (0.028)*

*P<0.05;**P<0.01; ***P<0.001; #Yates correction. UPDRS – United Parkinson’s Disease Rating Scale; GI – Gastrointestinal

Table 4

Comparison of demographic and clinical profile of those without (Group I) and with (Group II) lifetime psychiatric illness

Variable	Mean (SD)/Group I (n=112), n (%)	Mean (SD)/Group II (n=127), n (%)	T/χ2 (P)
Age of onset of Parkinson’s disease	57.3 (7.9)	51.8 (7.6)	−5.5 (<0.001)***
Duration of Parkinson’s disease (months)	43.9 (49.4)	85.3 (40.9)	7.0 (<0.001)***
Both Syndopa plus and Syndopa	59 (52.7)	35 (27.6)	15.7 (<0.001)***
UPDRS
UPDRS - mentation, behavior, and mood	5.6 (2.0)	9.2 (2.0)	−14.0 (<0.001)***
UPDRS - activities of daily living	17.5 (4.7)	29.2 (5.7)	−17.2 (<0.001)***
UPDRS – motor examination	19.2 (4.4)	31.7 (5.6)	−19.1 (<0.001)***
Total score in UPDRS (I+II+III)	42.3 (8.6)	70.1 (11.7)	−20.7 (<0.001)***
UPDRS - complications of therapy (past week)
Dyskinesia (%) days
<50	104 (92.9)	70 (55.1)	42.8 (<0.001)***
>50	8 (7.1)	57 (44.9)
Disability due to dyskinesia
No to moderate	97 (86.6)	76 (59.8)	21.3 (<0.001)***
Severe to complete	15 (13.4)	51 (40.2)
Painful dyskinesia
No to moderate	92 (82.1)	75 (59.1)	15.1 (<0.001)***
S-evere to marked	20 (17.9)	52 (40.9)
Early morning dystonia#-Yes	0	16 (12.6)	13.2 (<0.001)***
UPDRS - clinical fluctuations	77 (68.8)	54 (42.5)	16.5 (<0.001)***
Are “off” periods predictable? - Yes
UPDRS - clinical fluctuations	71 (63.4)	60 (47.2)	6.3 (0.012)*
Do “off” periods come on suddenly within a few seconds? - Yes
UPDRS - clinical fluctuations
For what proportion of the waking day is the patient “off” on average? (%) days
<50	79 (70.5)	104 (81.9)	4.3 (0.039)*
51-75	33 (29.5)	23 (18.1)
Other complications: GI symptoms - Yes No	39 (34.8)	84 (66.1)	23.4 (<0.001)***
Other complications: Sleep disturbances - Yes	112 (100)	127 (100)	5.2 (0.023)*
Other complications: Symptomatic orthostasis - Yes	52 (46.4)	90 (70.9)	14.7 (<0.001)***
UPDRS - modified Hoehn and Yahr staging#
<Stage 2.5	112 (100)	73 (57.5)	59.1 (<0.001)***
>Stage 2.5	0	54 (42.5)
UPDRS - Schwab and England Activities of Daily Living (percentage)	56.5 (8.4)	48.4 (4.8)	9.4 (<0.001)***
Physical comorbidity
Diabetes mellitus	8 (7.1)	21 (16.5)	4.9 (0.026)*

*P<0.05; ***P<0.001; #Yates correction. UPDRS – United Parkinson’s Disease Rating Scale; GI – Gastrointestinal; SD – Standard deviation

Relationship of depression with other variables is shown in Tables 5 and 6.

Table 5

Comparison of participants with current depression (major depression plus dysthymia) (Group I) and without current depression (Group II) (n=239)

Variable	Mean (SD)/Group I (n=42), n (%)	Mean (SD)/Group II (n=197), n (%)	T/χ2 (P)
Age of onset of Parkinson’s disease	53.2 (7.6)	59.0 (8.1)	−3.1 (0.002)**
Duration of Parkinson’s disease (months)	67.8 (51.6)	42.7 (36.5)	3.0 (0.003)**
UPDRS - mentation, behavior, and mood	9.9 (1.9)	7.0 (2.5)	−7.0 (<0.001)***
UPDRS - activities of daily living	33.0 (5.2)	21.8 (6.8)	−10.1 (<0.001)***
UPDRS - motor examination	34.6 (5.5)	24.0 (7.2)	−8.9 (<0.001)***
Total score in UPDRS (I+II+III)	77.5 (11.3)	52.7 (15.2)	−10.0 (<0.001)***
Dyskinesia (%) day
<50	19 (45.2)	155 (78.7)	19.6 (<0.001)***
>50	23 (54.8)	42 (21.3)
Disability due to dyskinesia
No to moderate	20 (47.6)	153 (77.7)	15.6 (<0.001)***
Severe to complete	22 (52.4)	44 (22.3)
Painful dyskinesia
No to moderate	17 (40.5)	150 (76.1)	20.9 (<0.001)***
Severe to marked	25 (59.5)	47 (23.9)
Early morning dystonia# - Yes	14 (33.3)	2 (1.0)	52.8 (<0.001)***
UPDRS - clinical fluctuations: Are “off” periods predictable? - Yes	11 (26.2)	120 (60.9)	16.8 (<0.001)***
UPDRS - Clinical fluctuations (for what proportion of the waking day is the patient “off” on average?)# (%) days
<50	41 (97.6)	142 (72.1)	11.2 (0.001)**
51-75	1 (2.4)	55 (27.9)
Other complications: GI symptoms - Yes	39 (92.9)	84 (42.6)	35.0 (<0.001)***
Other complications: Sleep disturbances - Yes	42 (100.0)	155 (78.7)	10.9 (0.001)**
Other complications: Symptomatic orthostasis - Yes	41 (97.6)	101 (51.3)	30.8 (<0.001)***
UPDRS - modified Hoehn and Yahr staging#
<Stage 2.5	13 (31.0)	172 (87.3)	62.9 (<0.001)***
>Stage 2.5	29 (69.0)	25 (12.7)
UPDRS - Schwab and England Activities of Daily Living (in percentage)	45.5 (6.3)	53.6 (7.4)	6.6 (<0.001)***
Mean score - short IQCODE	3.5 (0.4)	3.2 (0.6)	−2.7 (0.007)**
Total score ISI	20.8 (3.4)	17.3 (6.0)	−3.6 (<0.001)***

**P<0.01; ***P<0.001, #Yates correction. UPDRS – United Parkinson’s disease Rating Scale; SD – Standard deviation; IQCODE – Informant Questionnaire on Cognitive Decline in the Elderly

Table 6

Comparison of participants with lifetime depression (major depression, dysthymia) (Group I) and without lifetime depression (Group II)

Variable	Mean (SD)/Group-I (n=57), n (%)	Mean (SD)/Group-I (n=182)	T/χ2 (P)
Age of onset of Parkinson’s disease	53.6 (8.0)	58.1 (7.8)	(<0.001)***
Duration of Parkinson’s disease (months)	71.8 (51.3)	36.2 (33.7)	(<0.001)***
Patients on both Syndopa plus and Syndopa	14 (24.6)	80 (44.0)	6.8 (0.009)**
Patients on Syndopa plus	33 (57.9)	131 (72.0)	4.0 (0.046)*
UPDRS - mentation, behavior, and mood	9.4 (2.0)	6.9 (2.6)	−3.7 (<0.001)***
UPDRS - activities of daily living	31.1 (6.4)	21.5 (6.8)	4.9 (<0.001)***
UPDRS - motor examination	32.9 (6.0)	23.6 (7.3)	−6.6 (<0.001)***
Total score in UPDRS (I+II+III)	73.4 (13.3)	52.0 (15.2)	−9.5 (<0.001)***
Dyskinesia (%) days
<50	29 (50.9)	145 (79.7)	18.2 (<0.001)***
>50	28 (49.1)	37 (20.3)
Disability due to dyskinesia
No to moderate	30 (52.6)	143 (78.6)	14.6 (<0.001)***
Severe to complete	27 (47.4)	39 (21.4)
Painful dyskinesia
No to moderate	26 (45.6)	141 (77.5)	20.9 (<0.001)***
Severe to marked	31 (54.4)	41 (22.5)
Early morning dystonia# - Yes	14 (24.6)	2 (1.1)	38.3 (<0.001)***
UPDRS - clinical fluctuations	19 (33.3)	112 (61.5)	13.9 (<0.001)***
Are “off” periods predictable? - Yes
Other complications: GI symptoms - Yes	40 (70.2)	83 (45.6)	10.5 (0.001)**
Other complications: Symptomatic orthostasis - Yes	41 (71.9)	101 (55.5)	4.9 (0.027)*
UPDRS - modified Hoehn and Yahr staging
<Stage 2.5	27 (47.4)	158 (86.8)	38.6 (<0.001)***
>Stage 2.5	30 (52.6)	24 (13.2)
UPDRS - Schwab and England Activities of Daily Living (percentage)	47.0 (6.5)	53.8 (7.5)	6.1 (<0.001)***

*P<0.05; **P<0.01; ***P<0.001; #Yates correction. UPDRS – United Parkinson’s disease Rating Scale; SD – Standard deviation

Relationship of psychosis with other variables

When those with psychosis were compared with those without psychosis, those with psychosis had lower age of onset (P = 0.032*), longer duration of illness (P < 0.001***), higher scores on the UPDRS domains of mentation, behavior and mood (P = 0.001***), activities of daily living (P < 0.001***), and motor examination and total of these 3 domains (P = 0.001***). Higher proportion of those with psychosis had severe to complete disability due to dyskinesia (P = 0.038*), gastrointestinal symptoms (P = 0.037*), sleep disturbances (P = 0.044*), orthostatic (P = 0.004**), and sleep disturbances (P = 0.044*).

Relationship of anxiety disorders with other variables

When those with anxiety disorder were compared with those without anxiety disorder, higher proportion of those with anxiety disorder had diabetes mellitus (P = 0.01**), family history of PD (P = 0.007**), gastrointestinal symptoms (P = 0.019*), and more than 2.5 stages (P < 0.001***) as per the modified H and Y staging.

Those with anxiety disorder had higher scores on the UPDRS domains of mentation, behavior and mood (P < 0.001***), activities of daily living (P = 0.001***), motor examination (P < 0.001***), and total of these 3 domains (P < 0.001***). Lower proportion of those with anxiety disorder had predictable “off” periods (P = 0.037*).

DISCUSSION

In the present study, 17.5% of patients had current diagnosis of a depressive disorder and 23.8% of patients fulfilled the lifetime diagnosis of depressive disorder. In terms of type of depressive disorder, major depressive disorder was seen in 9.6% of patients and lifetime diagnosis of major depressive disorder was seen in 15.9% of patients. Diagnosis of dysthymia was made in 7.9% of cases. Existing literature suggest the prevalence of major depression in patients with PD to vary from 2.7% to 55.6%[131415161718192021] and 2.2% to 31.3%[1322] for dysthymia. Overall, the prevalence of clinically significant depressive features has varied from 2.7% to 89%.[132123] Findings of the present study are in the reported range for all the types of depressive disorders. Overall, in the present study, 25.4% had a current depressive disorder (major depressive disorder or dysthymia).

Existing literature does not support the association of depression in patients with PD with any of the sociodemographic variables except for higher prevalence of depression in females.[242526] However, majority of the studies have not reported female gender to be a risk factor for depression in patients with PD. Findings of the present study too support the same.[14272829]

In terms of clinical factors, literature suggest the association of depression with advanced/more severe disease,[2530] longer duration of illness,[30] early and late stage of disease,[15] motor disability,[31] bradykinesia,[3233] dystonia,[34] presence of tremor,[35] presence of motor fluctuations,[3031] more evidence of atypical parkinsonism,[31] gait and balance impairment,[32] younger age,[31] and higher daily doses of levodopa.[3031] Findings of the present study also support many of these associations. In the present study, depression was associated with significantly lower age of onset, longer duration of illness, had higher severity of illness as assessed by UPDRS, and dyskinesia for longer duration in a day. Further higher proportion of those with depression had severe to complete disability due to dyskinesia, painful dyskinesia, dystonia, gastrointestinal symptoms, sleep disturbances, and orthostasis. In addition, higher proportion of them had disease severity of more than 2.5 as per the modified H and Y staging. However, lower percentage of them had “off” periods lasting for 50%–75% of the day. No relationship was noted between depression and medications used for the treatment of PD. In terms of impact of depression, studies have consistently shown deterioration of scores on activities of daily living.[131431] Findings of the present study also suggest that the presence of any kind of depression at the time of assessment is associated with higher impairment in activities of daily living. Taken together, the findings of the prevalence of depression and severity of the same suggest that there is a need to routinely screen patients of PD for depression and those found to have depression must be treated adequately to improve the overall outcome of the disorder. If it is not possible to screen all the patients of PD for depression, at least those at high risk must be screened routinely using screening questionnaire and those found positive in the screening questionnaires must be evaluated further to confirm the diagnosis. It is also important to emphasize to the treating neurologist that if depression is not treated adequately, it can lead to higher level of impairment in activities of daily living.

In the present study, among the other psychiatric disorders, the single most common diagnosis was that of psychotic disorders, seen in 11.3% of patients at the time of assessment and 11.7% of patients in the lifetime. The prevalence of psychosis (or visual hallucinations) in the existing literature has varied from 15.8% to 75%.[23637] However, it is important to note that many of these studies have evaluated only the prevalence of certain symptoms such as visual hallucination rather than making a syndromal diagnosis. The slightly lower prevalence than that reported in the literature in the present study could be due to reliance on making a syndromal diagnosis, rather than focusing on symptoms of psychosis per se. In terms of risk factors, in the present study, those with psychosis had lower age of onset, longer duration of illness, and higher severity of illness as per the total UPDRS score. In addition, higher proportion of those with psychosis had severe to complete dyskinesia, gastrointestinal symptoms, sleep disturbances, orthostasis, clinical insomnia, and daytime sleepiness. When the relationship of psychosis and antiparkinsonian agents was evaluated, in two-third of the cases (64.9%), psychosis was associated with use of antiparkinsonian medications. Existing literature from developed countries have also identified similar risk factors.[38]

When all the anxiety disorders were taken together, the prevalence of anxiety disorders was 17.6%. Studies from other parts of the world have also reported prevalence of anxiety disorders to vary from 19.8% to 67%.[39] Findings of the present study are close to the lower level of prevalence reported in literature, and this could be possibly due to evaluation of anxiety disorder based on the structured interview in the present study. The most common anxiety disorders in patients with PD are panic disorder,[2] generalized anxiety disorder, and social phobia.[240] In the present study too, panic disorder (seen in 8.8% of cases) was the most common anxiety disorder seen in patients with PD, followed by generalized anxiety disorder (3.3%) and obsessive–compulsive disorder (3.3%). Only few patients had comorbid agoraphobia (2.9%). Although few studies suggest a correlation of higher level of anxiety with left-sided lesions, most studies have shown no relationship between severity of motor symptoms and levels of anxiety.[2541] In the present study too, higher proportion of those with anxiety disorder had disease severity of more than 2.5 as per the modified H and Y staging.

Other risk factors reported for anxiety disorder/symptoms in patients with PD include female gender,[28] younger age,[28] young onset PD,[40] more depressive symptoms,[28] worst sleep quality,[28] severity of PD,[41] postural instability,[41] gait dysfunction,[41] higher rates of motor fluctuations,[40] morning dystonia,[41] symptom clustering, and experience of dyskinesias.[41] Findings of the present study also support some of these associations. In the present study, higher proportion of those with anxiety disorder had higher income, had diabetes mellitus, family history of PD, had dyskinesia for more than 50% of the day, and gastrointestinal symptoms. Further, it was seen that those with anxiety disorder had higher severity of illness as per the assessment on UPDRS and more impairment in activities of daily living.

The present study has certain limitations. The study sample was recruited from the patients attending a neurology clinic. Hence, the study cannot be generalized to the patients living in the community. The study involved cross-sectional evaluation, very few patients who were drug naïve, and the study did not evaluate the phenomenology of various psychiatric disorders. Hence, there is a need for more extensive and longitudinal studies to evaluate patients attending the clinics and those living in the community.

CONCLUSIONS

The present study suggests that patients with IPD have high prevalence of psychiatric morbidity. Considering the prevalence of psychiatric morbidity, there is a need for active collaboration between the neurologists and psychiatrists to improve the outcome of patients with PD. Whenever a collaborative functioning cannot be ensured, the treating neurologist should use appropriate screening measures to evaluate the possibilities of these comorbidities. When a comorbid disorder is suspected, a suitable referral consultation must be sought.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.