Patient selection and questionnaire: The present observational study was conducted over a period of six months from March 2015 to August 2015 in Department of Psychiatry and Department of Oral Medicine, Yenepoya University, Managlore, Karnataka, India. Consecutive patients reporting to the psychiatry department and diagnosed with anxiety, depression, bipolar disorders and schizophrenia by an experienced psychiatrist were administered a valid and reliable questionnaire for assessment of xerostomia [5]. This questionnaire was developed by Dyasanoor S et al., to assess the severity of xerostomia and consisted of six questions with dichotomous response as yes or no [5]. Based on the answers to the questions the study population was classified as mild, moderate or severe xerostomia. The criteria for assessing the severity of the xerostomia are presented in [Table/Fig-1] [5].

Ethical clearance was obtained from the Institutional Ethics Committee prior to the initiation of the study. Written informed consent was taken from all the enrolled patients. A detailed case history was taken; the associated oral symptoms and clinical signs were recorded.

Pilot study was conducted on 50 randomly selected participants, to assess the validity (face, content) and reliability of the questionnaire. The reliability was assessed by measuring Cronbach’s alpha. Test-retest reliability was calculated using Intra-class Correlation Coefficient (ICC). The validity was assessed by correlating all questions with each other.

Subjects who answered affirmatively to at least one of the questions were recorded as having oral dryness. These patients were subjected to complete oral examination by a skilled oral diagnostician to check for dryness of lip and mucosa. Depending on the severity of the symptoms, xerostomia subjects were classified into mild, moderate and severe. One hundred patients of each groups suffering from anxiety, depression, bipolar disorders and schizophrenia- respectively were included as study groups. These subjects were selected using a consecutive sampling technique. Similarly, 100 healthy individuals reporting to Deprartment of Oral Medicine for routine oral screening with no known psychiatric disease were consecutively recruited as a control group. Each group was further divided into two subgroups according to the age as young-middle group (18 - 49 years) and an older adult group (50 - 77 years).

Exclusion criteria: The exclusion criteria included patients using tobacco and alcohol. Patients with known causes of xerostomia on radiotherapy, salivary gland diseases, medication and subjects with any other systemic disorders were excluded.

Dryness of lip and oral mucosa: Diagnosis was made when there was absence of a saliva coating over the dorsum of the tongue, buccal mucosa, labial mucosa and the absence of pooled saliva over the floor of the mouth. Lip dryness was recorded when upper or lower lip showed the characteristic shiny appearance and/or in presence of chapped lip [12].

Chi square test was used for comparison of xerostomia in all groups. A spearman correlation was done to assess the association between xerostomia to dryness of lips and mucosa. ANOVA was applied to find association between multiple groups. All the statistical analysis was done using Statistical Package for Social Sciences (SPSS) version 21.0. (Chicago, USA) and α-value was set at < 0.05.

Pilot Study: The internal consistency reliability coefficient (Cronbach’s alpha) for the questionnaire was 0.72. The coefficient of test-retest reliability measured by ICC was 0.73. Correlations between the items i.e., questions ranged between 0.32-0.45 (<0.50).

Prevalence of Xerostomia: Xerostomia was reported in 51% of anxiety, 47% of depression, 39% of schizophrenia, 41% of bipolar disorders, and 27% of controls. The majority of psychiatric patients had moderate to severe xerostomia, whereas in control group, mild xerostomia was noted in 13%, moderate xerostomia in 8% and severe xerostomia in 6%. More number of patients with anxiety reported xerostomia than patients with depression, bipolar disorder, schizophrenia and the control group [Table/Fig-2]. Comparison of xerostomia in all groups using chi square test (p<0.01) revealed statistically significant differences (p<0.05). Higher numbers of psychiatric subjects were found to have xerostomia as compared to those in the healthy group.

Xerostomia was higher in young adults (18-49) than old adults (50-77) and more in female patients than male patients. The difference between the two age groups was statistically significant (p<0.025). The gender difference was statistically significant in all groups (p<0.034) [Table/Fig-3].

Xerostomia and dryness of lip and mucosa: On clinical examination, the prevalence of dry lip was 18% in anxiety, 20% in depression, 15% in schizophrenia, 17% in bipolar disorders and 9% in controls. Dry mucosa was observed in 21%, 19%, 14%, 14%, and 8% of anxiety, depression, schizophrenia, bipolar disorders and controls respectively. Dry lip and mucosa was higher among the study groups than control group [Table/Fig-4].

A moderate to strong spearman correlation (r=0.72) was observed between xerostomia and dryness of lips and mucosa.

The questionnaires used in present study were shown to be closely associated with a resting salivary flow rate below 1ml/minute. Question No. 1 was related to the resting saliva production as it focused on the patient’s general feeling of oral dryness. The rest of the questions were mainly oriented at the stimulated saliva production during chewing and swallowing [5].

Studies proposed that psychological disturbances, emotional instability and personality modulation have a possible role in xerostomia [1,2]. Psychological alterations establish its impact on body by the multi-directional and close inter-relations among the nervous, immune and endocrine system [13,14]. The incidence of xerostomia in emotionally altered patients may be explained on the basis of various neurophysiologic, neurochemical and neurobiological changes associated with the psychosocial disorders. Since salivary glands are neurobiologically regulated by autonomic nervous system, processes influencing the levels of transmitter substances in this system affect the salivary gland function [12,15].

The alterations in cerebral blood flow and metabolism in psycho-social disorders leads to stimulation of lateral and paraventicular nuclei by amygdala. This in turn results in autonomic arousal and increase in plasma cortisol levels leading to alterated salivary secretion and flow. Also endocrinal changes like hyperactivity of hypophysis pituitary adrenal axis results in increased cortisol levels which in turn have xerogenic effects [16].

Prevalence of xerostomia in general populations have shown great variability, due to different definitions and instruments used to measure it. The prevalence of xerostomia in general population ranges from 10% to 46%, with a lower prevalence for men (9.7%–25.8%) than women (10.3%–33.3%) [8]. These results were consistent with present study results.

Aditya et al., evaluated the prevalence of xerostomia and burning sensation in patients with psychosocial disorder [11]. Schizophrenia was the commonest psychosocial disorder; followed by depression and alcohol withdrawal syndrome with psychosis. Prevalence of xerostomia and burning sensation was 43.5% and 9.5% respectively. These results were similar to present study but in our study however anxiety patient had higher xerostomia when compared to other psychiatric conditions.

Few researchers stated that ageing has no significant clinical impact on salivary secretion and flow rate. However, few authors reported that the prevalence of xerostomia was higher in middle-aged and elderly populations [8]. This may be explained by the fact that older people suffer more commonly with systemic diseases and are on multiple medications as compared to younger age group which may directly or indirectly cause xerostomia [17–19]. Hopcraft MS et al., in their review found that xerostomia was a prevalent condition found in approximately 1 of 5 people and further increases in older individuals [8].

In the present study, xerostomia was more prevalent in younger age group. The reason could be because of changing life style pattern and competitiveness especially in the urban youth, rising levels of stress associated with personal and professional life and lack of life skills to cope with them. This pattern of age distribution has also been observed by Kumar M et al., [20].

In present study female psychiatric patients had higher xerostomia when compared to the males. This could be because of major life changes in females due to exposure to xerogenic medications or menopause. Similar results were reported by previous studies [8,21,22].

Various studies on xerostomia in elderly population have reported varied prevalence between 28% to 63% [23–26]. A systematic review of population based research suggested prevalence in the community of approximately 20%, although this appears to be higher in older populations and the institutionalized. Most of those studies used subjects residing in hospitals and community dwelling [27].

In this study higher association between xerostomia and dryness of lip and mucosa was noted. On clinical examination, the prevalence of dry lip was 18% in anxiety, 20% in depression, 15% in schizophrenia, 17% in bipolar disorders, and 9% in controls. Dry mucosa was observed in 21%, 19%, 14%, 14%, and 8% of anxiety, depression, schizophrenia, bipolar disorders and controls respectively. These findings were less than reported by Berti-CoutoSde A et al., and Farsi NM et al. They reported 37.5% of dry lip and 3.2% dry mucosa in xerostomic patients [28,29].

In this study, the prevalence of xerostomia was higher than the previous studies. However, study did not include subjects having systemic diseases, under medication and radiotherapy. The actual prevalence rate of xerostomia was found to be greater than the reported rates and cross-sectional clinical surveys might probably underestimate the true prevalence rate because symptoms of xerostomia may not be present at the time of examination. The present observational study was conducted in a small sample. Further comparative studies with larger sample size would be required to make a clear distinction.

In this study xerostomia was detected more often in psychiatric patients than the healthy individuals with a sound mind. Xerostomia is now being recognized as an important risk factor for dental diseases and its impact on the quality of life of sufferers. Hence, provision of better oral health care of this often neglected group of patients should be the priority. It is the responsibility of the psychiatrist and dentist to effectively provide adequate dental treatment for people with psychiatric disabilities through interdisciplinary approach. Early recongnition and treatment of xerostomia in this group of population can improve the quality of life and prevent various other dental diseases associated with it.