The relationship between sleep disturbance and the course of anxiety disorders in primary care patients

Abstract

This study examined the relationship between sleep disturbance and the course of anxiety disorders in primary care patients. Participants were part of the Primary Care Anxiety Project (PCAP), a naturalistic, longitudinal study of anxiety disorders in primary care. Participants completed an intake evaluation and follow-up assessments at 6 months, 12 months, and annually thereafter. Only participants with sleep data at intake were included in the current study (n = 533). The majority (74%) reported experiencing sleep disturbance at intake. Those with a diagnosis of generalized anxiety disorder (GAD) or post-traumatic stress disorder (PTSD) were over 2 times more likely to have sleep problems. Sleep disturbance at intake did not relate to the longitudinal course of GAD, social phobia, panic disorder, or obsessive–compulsive disorder. However, it did predict the course of PTSD, controlling for comorbid major depressive disorder (MDD) and having more than one anxiety disorder diagnosis intake, those with sleep disturbance at intake being less likely to remit from PTSD in the 5 years of follow-up. By year 5, only 34% of those with sleep problems at intake remitted from PTSD whereas 56% of those without sleep disturbance remitted from the disorder. The findings suggest that sleep disturbance in PTSD may have prognostic significance and may be important to address in clinical interventions.

Introduction

Sleep disturbances, which can include difficulties with sleep onset, maintenance, or efficiency, are highly prevalent. Estimates suggest that over one-third of the general population experience sleep difficulties and 8–27% experience chronic or severe sleep problems (Ancoli-Israel and Roth, 1999, Leger et al., 2000, Bixler et al., 2002, Ohayon, 2002, Ohayon and Roth, 2003, Leger and Poursain, 2005). Sleep disturbances can have detrimental effects on physical health and overall functioning, leading to greater utilization of medical services (Idzikowski, 1996, Leger et al., 2002, LeBlanc et al., 2007). Sleep problems cost an estimated $30–35 billion dollars per year (Walsh and Engelhardt, 1995). Emotional functioning and quality of life are also adversely impacted by sleep disturbances (Gallup Organization, 1995, Hamilton et al., 2007, LeBlanc et al., 2007). A substantial portion of those with sleep problems (40–50%) have comorbid psychiatric disorders (Ford and Kamerow, 1989, Buysse et al., 1994, Breslau et al., 1996), and sleep disturbance has been hypothesized to be a risk factor for the development and maintenance of mood and anxiety disorders (Ford and Kamerow, 1989, Breslau et al., 1996, Weissman et al., 1997, Gillin, 1998, Gregory et al., 2005, Mellman, 2006).

Anxiety disorders are the most frequently occurring type of psychiatric disorder, with a lifetime prevalence estimate of 29% in the general population (Kessler et al., 2005). Individuals with anxiety disorders have considerable disability and impairment (Sherbourne et al., 1996, Roy-Byrne et al., 1999), along with high utilization of medical services (Katon et al., 1990, Simon et al., 1995, Roy-Byrne and Katon, 1997, Rice and Miller, 1998, Greenberg et al., 1999). Anxiety disorders are the most commonly seen mental health problem in primary care settings, with as many as one-third of primary care patients having significant anxiety symptoms (Fifer et al., 1994). The majority of individuals with anxiety disorders seek treatment from their primary care provider (Shear and Schulberg, 1995, Price et al., 2000, Young et al., 2001). Furthermore, there are high rates of comorbidity between anxiety disorders and major depressive disorder (MDD) (Brown et al., 2001, Zimmerman et al., 2002). Research shows that MDD typically develops after the onset of an anxiety disorder (Zimmerman et al., 2002). Once MDD is present, it seems to impact the course of the anxiety disorder, those with comorbid MDD being less likely to remit from an anxiety disorder than those without comorbid MDD (Bruce et al., 2005).

Studies have examined anxiety symptoms in those with sleep disturbances, as well as sleep problems in those with anxiety disorders. Among individuals with sleep disturbances, 42% report elevated levels of anxiety (Mellinger et al., 1985). Furthermore, there are higher rates of anxiety disorders (Ford and Kamerow, 1989, Buysse et al., 1994, Breslau et al., 1996), with one study finding that those with sleep difficulties were 17 times more likely to have clinically significant anxiety (Taylor et al., 2005). In particular, research has found that of the anxiety disorders, generalized anxiety disorder (GAD) has the highest comorbidity rate with insomnia, which is not surprising given that sleep disturbance is included in the diagnostic criteria for the disorder (Ohayon et al., 1998, Monti and Monti, 2000). In individuals with GAD, 48% report difficulty with sleep onset and 64% with sleep maintenance (Belanger et al., 2004). Frequent awakenings and poor sleep quality are also characteristic of posttraumatic stress disorder (PTSD) (Mellman and Davis, 1985, Mellman et al., 1995, Neylan et al., 1998, Lamarche and De Koninck, 2007). Estimates suggest that 70% of individuals with PTSD experience such problems (Ohayon and Shapiro, 2000). Furthermore, sleep difficulties appear to play a role in the development of the disorder, with research showing that 72% of individuals who have sleep problems within 1 month of the trauma develop PTSD (Harvey and Bryant, 1998). Likewise, studies have shown that when sleep disturbance is successfully treated in individuals with the disorder, the PTSD symptoms improve (Youakim et al., 1998, Krakow et al., 2000, Krakow et al., 2001, Krakow et al., 2002). Sleep disturbances have also been reported in panic disorder (Anderson et al., 1984, Mellman and Uhde, 1989, Stein et al., 1993a, Arriaga et al., 1995, Overbeek et al., 2005). Relatively few studies have examined sleep in social phobia (Stein et al., 1993b, Brown et al., 1994) and obsessive–compulsive disorder (OCD) (Insel et al., 1982, Hohagen et al., 1994, Arriaga et al., 1995, Robinson et al., 1998), and the findings with these disorders have been inconsistent.

Although sleep disturbance and anxiety disorders appear to be related, and are both highly comorbid with MDD, the exact nature of the relationship remains unclear. It is difficult to ascertain whether sleep problems play a role in the development of anxiety disorders, or whether sleep difficulties are in fact a result of, or symptom of, anxiety. Some have found that chronic insomnia precedes and predicts later development of anxiety symptoms (Neckelmann et al., 2007), whereas others have found that onset tends to occur either at the same time or the anxiety disorder precedes the development of sleep difficulties (Ohayon and Roth, 2003). The majority of past studies on sleep disturbance and specific anxiety disorders have not controlled the effects of comorbid MDD, and no published research exists examining the relationship between sleep difficulties and the course of anxiety disorders over time.

The purpose of the current study was to examine the relationship between self-reported sleep disturbance and anxiety disorders using data from the Primary Care Anxiety Project (PCAP). PCAP is a naturalistic, longitudinal study of anxiety disorders in primary care patients. The current study sought to examine predictors of self-reported sleep disturbance, including demographic variables (age, gender, race, marital status, and education), anxiety disorder diagnoses (GAD, PTSD, social phobia, panic disorder, and OCD), and comorbid conditions (having more than one anxiety disorder diagnosis, MDD, alcohol/substance use disorders, and medical problems). The study also examined the relationship between sleep disturbance and the longitudinal course of anxiety disorders. More specifically, the study examined whether sleep disturbance at intake predicted remission from GAD, PTSD, social phobia, panic disorder, and OCD during the 5-year follow-up period, controlling for comorbid MDD and presence of additional anxiety disorder diagnoses.