Group that receives the smartphone-based serious game intervention and receives technical support

Group that does not receive any treatment

Smartphone-based serious game intervention consists in the use of a serious game designed specifically to improve depressive symptoms. The psychological content consists of CBT intervention with the following psychotherapeutic components: Motivation for change, Psychoeducation, Cognitive Flexibility, Behavioural Activation, and positive psychotherapeutic strategies. To encourage physical activity, the serious game incorporates a mixed reality through physical activities such as taking a walk in real life affects aspects inside the game.

The PHQ-9 is the depression module of the self-administered version of the PRIME-MD diagnostic instrument for common mental disorders. The PHQ-9 consists of 9 items ranging from "0" (not at all) to "3" (nearly every day). It has a dual-purpose instrument since it can establish both depressive disorder diagnoses and grade depressive symptom severity. Scores can range from zero to 27. Scores of 15 or greater indicated major depression.

The BDI-II is widely used to detect and assess the severity of depressive symptoms. The BDI-II consists of 21 multiple-choice items ranging from 0 to 3. It covers the different symptoms of major depression disorder in the DSM-IV. Scores can range from zero to 63. Scores greater than 29 mean major depression. The BDI-II has high internal consistency (alpha = 0.76 to 0.95) and for the Spanish version (alpha = 0.89) (Sanz, 2003)

The PANAS is used to measure trait and state affectivity. The PANAS consists of 20 items divided in two independent 10-item dimensions to assess positive affect (PA) and negative affect (NA). Each item rated on a 5-point Likert-type scale. Low levels of PA predict the onset depreesion, reduce positive emotions, and increase the severity of depressive symptoms.Patients with more comorbid diagnoses had significantly higher NA and lower PA. It is brief, reliable, and has shown excellent internal consistency (alpha = 0.84 to 0.90) and convergent and divergent validity. The Spanish version has also shown high internal consistency (alpha = 0.87 and 0.89 for PA and NA in men, respectively, and alpha = 0.89 and 0.91 for PA and NA in women, respectively (Díaz-García, 2020).

The OASIS is used to assess the severity and frequency of anxiety symptoms. Moreover, the scale provides information about behavioral avoidance and functional impairments in pleasurable activities, work, school or social relationship interference related to these symptoms in the last week. The OASIS consists of a 5-item self-report measure rated from 0 to 4 and are summed to obtain one total score. OASIS score of 8 or above would be indicative of a probable anxiety disorder. It has demonstrated strong psychometric properties with good internal consistency (alpha = 0.86), as well as test-retest reliability (K = 0.82) and convergent validity (Norman, 2006; Campbell-Sill, 2009; Norman, 2011).

he SUS is used to measure the usability of a software collecting the user's opinion. The SUS consists of a questionnaire of 10 items with 5 answer options rated from "o" (strongly disagree) to "4" (strongly agree)is a brief, reliable scale for measuring the usability of a program. It consists of a 10-item questionnaire with 5 response options, from 0 ("strongly disagree") to 4 ("strongly agree"). It could indicate that the user has had technical difficulties with the program. The Spanish version has been used in several research studies (Botella, 2016; Campos, 2018) and its validation process is currently ongoing.