Stimulus control for insomnia: A systematic review and meta-analysis.

This systematic review and meta-analysis investigated the effectiveness of **Stimulus Control (SC)** as a standalone treatment for insomnia. SC is a behavioral therapy based on the idea that difficulty falling asleep can be due to associating the bed and bedroom with activities incompatible with sleep (e.g., worrying, watching TV). The goal is to re-establish the bed and bedroom as cues for rapid sleep onset.

The specific rules of Stimulus Control, as developed by Bootzin and colleagues and commonly used in trials, are:

1. **Lie down, intending to go to sleep only when you are sleepy.**

2. **Do not use your bed for anything except sleep; that is, do not read, watch television, eat, or worry in bed.** Sexual activity is the only exception, after which instructions are to be followed when intending to sleep.

3. **If you find yourself unable to fall asleep, get up and go into another room.** Stay up as long as you wish and then return to the bedroom to sleep. The goal is to associate your bed with falling asleep quickly; if you are in bed more than about 10 minutes without falling asleep, get out.

4. **If you still cannot fall asleep, repeat Step 3.** Do this as often as necessary throughout the night.

5. **Set your alarm and get up at the same time every morning irrespective of how much sleep you got during the night.** This helps establish a consistent sleep rhythm.

6. **Do not nap during the day.**

The study compared SC against two types of comparators:

**Passive comparators:** These typically included waitlist control groups or no-treatment conditions.

**Active comparators:** These included other established treatments for insomnia, such as relaxation techniques or general sleep hygiene advice.

The primary **outcome measures** were self-reported sleep diary variables:

**Sleep Onset Latency (SOL):** The amount of time it takes to fall asleep.

**Total Sleep Time (TST):** The total duration of sleep.

**Number of Awakenings (NOA):** The frequency of waking up during the night.

The meta-analysis synthesized data from **11 individual studies** (8 of which were included in the quantitative meta-analysis) that investigated stimulus control. All included studies focused on **adults** who met criteria for **insomnia disorder** or reported significant sleep difficulties. The majority of these studies were published between 1978 and 1998, indicating that the evidence base for standalone SC is largely historical. The specific demographics (e.g., age range, gender distribution, specific health conditions) of the participants varied across the included studies, but the overall population was adults experiencing insomnia.

The efficacy of stimulus control was measured using **self-reported sleep diary measures**. Participants in the individual studies typically completed daily sleep diaries to record:

**Sleep Onset Latency (SOL):** The time from getting into bed with the intention to sleep until actually falling asleep.

**Total Sleep Time (TST):** The total duration of sleep obtained during the night.

**Number of Awakenings (NOA):** The count of times they woke up after initially falling asleep and before their final wake-up time.

These self-reported measures are standard in sleep research and clinical practice for assessing subjective sleep experience, though they can be subject to recall bias and may not always perfectly align with objective measures like polysomnography or actigraphy.

This study was a **systematic review and meta-analysis**, which means it systematically identified, evaluated, and synthesized findings from multiple individual studies on a specific topic. This design sits at the top of the evidence hierarchy, as it combines data from many studies to provide a more robust estimate of an intervention's effect than any single study could.

**Search Strategy:**

Four project-independent librarians conducted a systematic search in November 2022 across **six online bibliographic databases**: Medline (Ovid), Psycinfo (Ovid), Embase (Elsevier), Cinahl (Ebsco), Web of Science (Clarivate), and Dissertations and Theses (ProQuest).

The search used specific MeSH terms and keywords related to insomnia and stimulus control.

The first author also hand-searched the reference lists of recent systematic reviews and meta-analyses on CBT-I, as well as the reference lists of studies included in the current review, to ensure comprehensive coverage.

**Selection Procedure:**

The initial database searches yielded 3352 records, which were reduced to 1708 after removing duplicates.

These records were screened, and 80 full-text articles were assessed for eligibility.

**Inclusion criteria** for studies were:

* Randomized controlled trials (RCTs) or experimental designs from which outcome data per group could be extracted.

* Participants were adults with insomnia.

* Stimulus control was used as a standalone treatment (this was a key distinction from previous reviews that included SC combined with other therapies like sleep hygiene).

**Exclusion criteria** included: not an appropriate design, not a peer-reviewed article, not an empirical paper, insufficient information, intervention not *only* stimulus control, or not individuals with sleep difficulties.

Ultimately, **11 studies were included in the qualitative synthesis** (review of characteristics), and **8 of these were included in the quantitative synthesis (meta-analysis)**.

**Statistical Approach:**

A **random effects model** was used to calculate the standardized mean difference, expressed as **Hedge's g**, at post-treatment and follow-up. Hedge's g is a measure of effect size that indicates the difference between two groups in terms of standard deviations, adjusted for small sample sizes.

A test for **heterogeneity** (how much the results varied across studies) was conducted.

**Forest