The purposes of this study are a) to investigate the effect of a personalized and computerized cognitive stimulation program on sleep quality, cognitive performance, and quality of life; and b) verify if cognitive stimulation can be used as a non-pharmacological alternative to improve the quality of sleep in individuals who have insomnia.

Phase I/II was designed to determine the safety of the training, the maximum tolerated training time per session, and the needed training sessions to obtain significant cognitive performance improvement prior to beginning with the cognitive stimulation intervention program (Phase III).

Phase I/II

Through a 3+3 design, a dose-escalation trial will be set. Participants will be tested across subsequent training blocks of 15 minutes each, reporting experienced fatigue or adverse effects after every block. The safe training dose will be set to a block before extreme fatigue or a notable adverse effect has been reported by two or more participants.

Once a safety training time has been established, 20 participants will engage in a 15-day training effectiveness assessment. An evaluation day and a training day will be interspersed so that participants will complete a total of 7 training sessions (days 2, 4, 6, 8, 10, 12, and 14) and 8 evaluation sessions (days 1, 3, 5, 7, 9, 11, 13, and 15).

A psychologist will be supervising every step of the process at all times.

Phase III

A total of 120 persons with insomnia will undergo an 8-week cognitive stimulation program, five consecutive days per week. Eligible participants will be randomized in a 1:1 ratio to an intervention or control group. Activities duration per day will be as set on phase I.

This final phase is set to be an online home-based stage, although the responsible psychologist will periodically contact participants via telephone.

Inclusion Criteria:

• Be diagnosed by Insomnia Disorder [307.42 (F51.01)]:

A. A predominant complaint of dissatisfaction with sleep quantity or quality, associated with one (or more) of the following symptoms:

1. Difficulty initiating sleep. (In children, this may manifest as difficulty initiating sleep without caregiver intervention.)
2. Difficulty maintaining sleep, characterized by frequent awakenings or problems returning to sleep after awakenings. (In children, this may manifest as difficulty returning to sleep without caregiver intervention.)
3. Early-morning awakening with inability to return to sleep.

B. The sleep disturbance causes clinically significant distress or impairment in social, occupational, educational, academic, behavioral, or other important areas of functioning.

C. The sleep difficulty occurs at least 3 nights per week.

D. The sleep difficulty is present for at least 3 months.

E. The sleep difficulty occurs despite adequate opportunity for sleep.

F. The insomnia is not better explained by and does not occur exclusively during the course of another sleep-wake disorder (e.g., narcolepsy, a breathing-related sleep disorder, a circadian rhythm sleep-wake disorder, a parasomnia).

G. The insomnia is not attributable to the physiological effects of a substance (e.g., a drug of abuse, a medication).

H. Coexisting mental disorders and medical conditions do not adequately explain the predominant complaint of insomnia.

Exclusion Criteria:

• Have another sleep-wake disorder (e.g., narcolepsy, restless leg syndrome, a breathing-related sleep disorder, a circadian sleep-wake rhythm disorder, a parasomnia).
• Presence of a relevant medical, psychiatric or neurological disorder.
• Significant visual or motor impairments.
• History of alcohol or drug abuse or dependence.
• Caffeine consumption (more than 150mg per day, that is, approximately 3 cups of espresso or a cup of American coffee).
• Alcohol consumption (more than 250ml per day, that is, around a pint of beer, a glass of wine, or a shot of liquor).
• Use of medications with stimulant action, except sedatives or hypnotics prescribed for sleep.

Due to the institutional restrictions that regulate the data protection of patients in the Spanish public health system, it is not possible for the investigators to share any individual participant data.

Participants will be randomly assigned to one out of two groups (control/experimental).

The activities presented to Group 1 (experimental group) will target executive functions skills and will be automatically adjusted in difficulty and requirement according to each participant's performance so that a maximum cognitive effort is always required.

The activities for Group 2 (active control group) will be of constant difficulty throughout the intervention and will not target the intended cognitive processes (namely, they will target orthogonal unrelated aspects).

Participants and researchers are blind to whether they are in the intervention or the control group. In this way, placebo or waiting-list effects are avoided.