CBT for Insomnia in Patients with High and Low Depressive Symptom Severity: Adherence and Clinical Outcomes

Prior to participation in the CBTI group treatment program, patients were evaluated by a physician or clinical psychologist board certified in sleep medicine or behavioral sleep medicine. Patients who were referred to the program presented with an initial complaint of insomnia. Because the rating of CBTI components was completed at the last treatment session, the sample consists only of treatment completers. Among those who consented and were included in the archival dataset, 301 completed the Beck Depression Inventory (BDI) at baseline at the last group session, when the posttreatment BDI was administered, and thus constituted the sample for this study. Those with comorbid psychiatric, sleep, or medical disorders, as well as those with concomitant use of sleep or other medications, were not excluded. Patients were not required to discontinue hypnotics prior to or during treatment. The sample for this study represents 45% of the total number of patients in the database who provided baseline BDI data. Reasons for missing data were: not attending the last treatment session, when posttreatment data were collected or not completing the posttreatment questionnaires. Patients not included in this study did not differ significantly on age, depressive symptom severity, or insomnia severity (all p-values > 1.0) from those who were included in the study sample.

Treatment consisted of 7 (90-min) sessions of group CBTI delivered in a structured sequence. The first 5 sessions were delivered weekly, and the last 2 sessions occurred biweekly. Session 1 consisted of education about CBTI, orienting patients to the program, mini intakes, and goal setting. The remaining 6 sessions of this structured intervention consisted of psychoeducation about sleep and sleep hygiene (Session 2), stimulus control treatment and sleep restriction treatment (introduced in Session 3 and refined in Sessions 5 and 6), relaxation training (i.e., deep breathing exercises and other relaxation strategies for calming the mind prior to sleep initiation; Session 6), scheduled worry time (introduced in Session 3 and 4 and revisited in subsequent sessions), cognitive restructuring (discussed to some degree at each session), and relapse prevention (Session 7). Depressive symptoms were not directly addressed, except when they directly interfered with adherence to the behavioral components of CBTI. For example, when anhedonia made it difficult to adhere to the prescribed out of bed time, the therapist worked with the patient to identify and schedule morning activities to assist the patient in getting out of bed at the prescribed time.

To test whether CBTI was more effective in reducing insomnia among patients with low depression severity compared to high depression severity, the sample was split using a validated BDI cutoff score for probable depressive disorder¹² as follows: a high depression group (HiDep) consisted of patients whose baseline BDI was ≥ 14 (N = 120), and a low depression group (LowDep) consisting of patients whose baseline BDI was < 14 (N = 181). This categorization was performed post hoc at the analysis stage. Thus, patients in both groups were not separated and received the same group treatment. A series of repeated measures ANOVAs were used to compare the change in ISI (the primary sleep outcome) and four diary-based sleep measures (latency to sleep onset, time awake after sleep onset, total sleep time, and sleep efficiency) from pre- to post-treatment, with Hi/LowDep as a between-subject factor. An independent t-test was employed to compare the HiDep and LowDep groups on the TSS Insomnia item (secondary sleep outcome). Independent t-tests were used to compare the HiDep and LowDep groups on overall treatment satisfaction (mean TSS items), which provided a measure of clinical significance, and enabled analysis of individual TSS items.

The differential effects on adherence to and perceived helpfulness of specific CBTI treatment components were assessed with a series of independent t-tests, comparing the HiDep and LowDep groups on adherence with and perceived helpfulness of specific CBTI treatment components as measured by the TCAS. To minimize type I error, we first compared group differences in each of the four treatment components. When a group difference for a given component emerged, it was followed by testing group differences in each of the specific therapeutic elements constituting this component.

To assess the impact of CBTI on depressive symptom severity, the analysis was restricted to the HiDep group. Pre- to post-treatment change in depression severity (BDI total scores, computed without the sleep item) was assessed with a paired t-test. The sleep disturbance item on the BDI (item 16) was deleted from the total BDI score to allow for assessment of CBTI effects on depressive symptom severity beyond disturbed sleep. Pre- to post-treatment change in suicidal ideation, assessed with BDI item 9, was analyzed using Wilcoxon Signed Ranks Test among the 65 individuals with a non-zero score on the BDI suicide item (9) at pretreatment.

Figure 1 describes change in ISI scores in the 2 groups. There was no significant group (HiDep/LowDep) by time (pre- vs posttreatment) interactions (p = 0.61) on the change in ISI; but there were significant main effects for both time (p < 0.0001) and depression group (p < 0.001); this indicates that there was an overall reduction in pre- to posttreatment ISI score, and that the HiDep group had significantly higher ISI scores (p < 0.0001) throughout treatment. Thus, HiDep patients showed higher insomnia severity than LowDep patients at both pre- and posttreatment, yet benefited from group CBTI equally. Partial remission (≥ 7 point decrease in ISI) was attained by 59.8% of patients in the LowDep group and 60.4% of the HiDep group (Fisher exact p-value = 0.55). Marked improvement (≥ 9 point decrease in ISI) was attained among 39.0% of patients in the LowDep group and 43.8% in the HiDep group (p = 0.36). Table 4 summarizes sleep diary data at baseline and posttreatment. A series of repeated measures analysis of variance revealed a significant decrease in latency to sleep onset and time awake after sleep onset, and a significant increase in sleep efficiency, with all p-values < 0.0001; no significant change in total sleep time (p = 0.22) was observed. There was no main effect for group or group × time, with all p-values > 0.2. Use of medications for sleep was reduced from 69.7% at baseline to 50.9% at the end of treatment, with no statistically significant difference between the groups (p = 0.24). Among those who used medications for sleep, the number of days medications were used dropped from 5.9 days per week at baseline to 5.5 at posttreatment, again with no significant group difference (p = 0.29). There were no significant differences between groups on TSS total score or individual items (all p-values > 0.14). The majority of participants reported that treatment made symptoms somewhat or a lot better (91% for insomnia, 65% for energy level, 59% for work productivity, 72% for coping, 68% for life enjoyment, 75% for hopefulness, 57% for self-esteem, and 60% for mood).

HiDep patients reported following the Behavioral Component to a lesser extent than LowDep patients (p = 0.004). Of the 4 items defining the Behavioral Component, HiDep participants reported poorer adherence to a fixed rise time (p < 0.0001) and to decreasing amount of time spent in bed (p = 0.016) compared to LowDep patients. In contrast, groups did not significantly differ in the extent to which they endorsed the Cognitive Component (p = 0.07); but patients in the HiDep group reported lower change in their expectations about sleep (p < 0.05). Table 5 summarizes the extent to which each of the treatment elements were followed. Greater adherence to the Cognitive and Behavioral Components were associated with lower posttreatment ISI scores (r = −0.34, p < 0.0001; and r = −0.27, p = 0.002, respectively)

Table 6 summarizes the perceived helpfulness of each of the treatment elements. There were no significant observed differences between HiDep and LowDep patients in the perceived helpfulness of the 4 treatment components (Behavioral, Cognitive, Nonspecific, and Sleep Hygiene Components; all p-values ≥ 0.38). The rank order of the perceived helpfulness of these 4 components (Nonspecific, Cognitive, Behavioral, and Sleep Hygiene) did not differ between the LowDep and HiDep groups.

There was a significant reduction in depressive symptom severity (BDI total score after excluding the sleep item) in the whole sample (p < 0.0001) from 12.54 (SD = 7.27) pretreatment to 7.91 (SD = 6.20) posttreatment. Among HiDep patients, depressive symptom severity decreased from 19.74 (SD = 5.33) pretreatment to 12.02 (SD = 6.73) posttreatment (p < 0.0001, Cohen’s d = 1.45). A Wilcoxon signed ranks test revealed that CBTI elicited a statistically significant change in suicidal ideation pre- to posttreament (Z = −5.925, p < 0.001). According to analyses of rankings, 40 participants endorsed higher pretreatment suicidal ideation scores (range 0-3) than following treatment; 1 participant endorsed a higher suicide score following treatment (range 0-1); and 247 participants showed no change in pre to posttreatment suicidal ideation symptoms (range 0-1). Among the 65 participants who scored > 0 on BDI Item 9 for suicide ideation, pretreatment scores on the suicide ideation item were 1.10 (SD = 0.35) at baseline and 0.45 (SD = 0.50) at the end of treatment (p < 0.0001; Cohen’s d = 1.83); 45% of patients with suicide ideation at pretreatment no longer endorsed it at the posttreatment. At baseline, 23% scored > 0 on the BDI suicide item (21 % scored 1, 2% scored 2 or 3); whereas at posttreatment only 10% scored 1 (0% scored above 1). Table 3 provides descriptive statistics for BDI pre and posttreatment.

We observed that adherence to two Behavioral Component elements of CBTI, keeping a fixed rise time and restricting time in bed, and one Cognitive Component treatment element, changing expectations about sleep, were lower among patients with greater depression severity. These findings suggest that greater attention to these three aspects of CBTI may enhance its efficacy among individuals with depressive illness. Possible adaptations may include: (a) scheduled activities in the morning and in the evening to increase adherence to morning rise time and facilitate TIB restrictions; and (b) greater attention to cognitive factors, such as patients’ beliefs about sleep and insomnia. These recommendations are congruent with effective psychological treatments of depression, such as cognitive therapy for depression, cognitive behavioral therapy for depression, and behavioral activation therapy, which strategically target dysfunctional cognitions, inactivity, and anhedonia.^11,17-19 Previous recommendations for adaptation of CBTI when applied to insomnia comorbid with depression²⁰ were based largely on clinical understanding of major depressive disorder, including how its symptoms may negatively impact sleep-related behaviors and cognitions. Data from the current study suggests that incorporating behavioral activation and cognitive therapy techniques into CBTI may further improve outcome for patients with elevated depressive symptoms.

We found that CBTI leads to significant reduction in depressive symptom severity (excluding the sleep symptom) among those with high depressive symptom scores. Results also revealed that CBTI was associated with a significant symptom reduction in suicidal ideation among those who endorsed suicidal ideation at baseline. Results furthermore suggested that CBTI positively impacts several non-sleep related aspects of depression, including enjoyment, hopefulness, self-esteem, coping with stress, work productivity, mood, and energy levels; and these beneficial effects did not differ according to depression severity. Perceived improvements in enjoyment, hopefulness, self-esteem, coping with stress, mood, and suicidal ideation suggest that the effects of CBTI on depression extend beyond simply improving just its target (sleep), through yet unknown mechanisms. We propose that improvements in sleep and hence energy may contribute to hopefulness, ability to cope with stress, and increased productivity, and translate into improvements in self-esteem and mood. Though plausible, this possibility awaits direct testing. Our findings are consistent with emerging data on clinical improvements in general functioning, such as depressive symptoms and perceived general health among older adults recruited from the community and primary care.²¹ This recent study and our current findings demonstrate that in clinic samples, CBTI offers beneficial effects on symptoms that are not directly targeted by the therapy itself. The improvement in depressive symptom severity we found is consistent with previous studies, most uncontrolled, that examined the effects of CBTI on depressive symptom severity. These studies are reviewed in a report from a workshop that evaluated whether the effective management of sleep disorders could reduce both concurrent depressive symptoms and the risk of developing subsequent depression.²² Seven of the eight studies that were reviewed found that CBTI improved both insomnia and depressive symptoms. The exception is a study by Lichstein and colleagues who studied patients with insomnia secondary to medical and psychiatric conditions. This study found that, although CBTI was effective in reducing insomnia symptoms, it did not reduce depressive symptom severity.²³

A growing body of research suggests that disturbed sleep confers elevated risk for suicidal behaviors.^24-27 Sleep complaints are in fact listed among the top 10 warning signs of suicide by the Substance Abuse and Mental Health Services Administration (SAMHSA). To our knowledge, this is the first investigation to show that a sleep-focused therapy leads to a significant decrease in suicidal ideation. Of note, the observed effect size for this finding was large (d = 1.83), suggesting that CBTI results in a clinically meaningful reduction in suicidal ideation. Unlike many other suicide risk factors (e.g., past suicide attempt), insomnia constitutes a modifiable risk factor for suicide. Our findings suggest that CBTI could enhance suicide prevention among patients with insomnia—an assertion that needs to be tested in a randomized controlled fashion, using a more rigorous assessment of suicidal symptoms than the single-item assessment used in the current study. If proved effective at reducing suicide risk, sleep-based suicide prevention may be appealing to patients because sleep disturbance is less stigmatizing than depression.

Several limitations should be noted in the present study. First, this investigation was not a controlled trial and assessed treatment completers only. Second, we evaluated adherence to individual CBTI treatment components based on retrospective self-ratings, rather than measures derived from prospective sleep diaries or actigraphy. However, we assessed adherence with some important aspects of treatment that cannot be assessed with actigraphy or standard sleep diary entries, such as going to bed only when sleepy. We believe that the best way to assess adherence is through a combination of measures. Adherence to cognitive elements may be more difficult to qualitatively assess and quantify compared to behavioral treatment recommendations. Further refinement of the assessment of cognitive components is needed. Third, all sleep measures were subjective. With a shared method of variance, we cannot rule out the possibility that participants who reported better outcomes may have been more likely to report greater adherence to treatment. Lastly, our sample consisted of outpatients presenting to a sleep clinic for insomnia treatment. No exclusion criteria were used. Moreover, diagnosis of major depressive disorder was not assessed. While limiting internal validity, use of a clinical sample may be considered a strength of the study because it increases external validity and generalizability of study findings. Additional research is warranted to test if the results will extend beyond the presence of elevated depressive symptom severity—to patients with a comorbid depressive disorder and insomnia.