Table 2 indicates that the subjective sleep-onset latency was longer
than the measurements recorded objectively. Sleep-onset latency that
exceeded 30 minutes recorded in the daily sleep log was greater than
the sleep-onset latency measured using actigraphy (Table 3). This result
was consistent with the results determined in a previous study, which
indicated that patients with bipolar disorders tended to overestimate
their sleep-onset latency (Harvey, Schmidt, Scarnà, Semler, & Goodwin,
2005). Because depression can cause negative biases when processing
information (Nolen-Hoeksema & Hilt, 2008), the time perception of patients with depression might not be as accurate as that of people without depression. Although depression patients might feel that they spent
a long time falling asleep, the length of time they actually required to fall
asleep was not that long.