This intervention will act as a control condition. During the waiting period (12 weeks) participants assigned to this condition will continue receiving Treatment As Usual at the Royo Villanova Hospital. It consists of regular contact with doctors to monitor the physical symptomsof long COVID-19.

After the 12 weeks, participants in this conditions will join the experimental group and they will receive the psychological intervention following the same procedure described for the experimental condition.

It is composed by 49 items that evaluates the transdiagnostic profile of Emotional Disorders, which is composed of nine dimensions: neurotic temperament, positive temperament, depressed mood, somatic anxiety, arousal activation, social anxiety, intrusive cognitions, traumatic re-experiencing, and avoidance.

Evaluation through 36 items of difficulties in emotional regulation by means of 5 subscales: lack of control, rejection, interference, inattention and emotional confusion. Higher scores indicate greater difficulties in emotion regulation.

It is composd by 5 items assessing self-perceived health status. Higher scores indicate better quality of life.

This scale evaluates, through 15 items, distress tolerance in the following dimensions: 1) Tolerance: perceived ability to tolerate emotional distress; 2) Appraisal: subjective assessment of distress; 3) Absortion: attention absorbed by negative emotions; 4) Regulation: strategies to alleviate distress.

This scale consists of 14 items designed to measure the level of perceived stress in daily life over the past month. The items are rated from 0 to 4, where 0 is "never" and 4 is "very often." Higher total scores indicate greater perceived stress.

the adaptation made for this study includes 6 of the 8 items of the CSQ-8 (perceived quality, adequacy to previous expectations, recommendation of the treatment to friends or family, usefulness of the techniques learned, general satisfaction with the intervention and probability that they will choose an intervention of this type again) and one additional item related to the discomfort generated by the intervention. Likewise, a change has been made in the Likert response scale from 4 points in the original (0 = "Bad / Not at all" to 4 = "Excellent/Very Much") to 11 in the current one (0 = "Bad / Not at all to 10 = "Excellent/Very Much"). Higher scores represent greater satisfaction with the treatment.

This questionnaire has been elaborated ad hoc. It is composed of 7 questions; one general question that evaluates the usefulness of the program to improve emotional regulation and six specific questions that separately evaluate the usefulness of each of the techniques that are worked on in the different modules of the UP to better regulate emotions . The response scale ranges from 0 (not at all) to 10 (very much). Higher scores represent higher satisfaction with the treatment.

Brief neuropsychological test designed to assess mild cognitive impairment. It evaluates multiple cognitive domains, including visuospatial skills, memory, working memory, attention, concentration, language, executive functions, and orientation. It has a maximum score of 30 points, with a common cutoff score of 25 to identify potential cognitive deficits. A score of 25 or lower is considered indicative of cognitive impairment.

This cognitive test presents a coding matrix in which the digits from 1 to 9 are paired with a symbol. On the same sheet, a series of digits is displayed with a blank space where participants must draw the corresponding symbol. The task must be completed as quickly as possible, with a 120-second limit to match the symbols with their respective numbers. If participants fail to complete the first four lines within the allotted time, they are given additional time to ensure they gain enough experience with the digit-symbol association. The tota score is based on the number of symbols correctly paired within 120 seconds (maximum score: 133). Immediately after completing the task, the researcher provides the participant with a new sheet containing the digits from 1 to 9 arranged in two lines. In this second part, participants must complete the blank spaces by drawing from memory the symbols corresponding to each number, with no time limit.

The direct order digit task of this subtest evaluates verbal short-term memory and consists of a numeric recall task that measures the mechanical repetition of a sequence of numbers. The reverse order digit task assesses verbal working memory and requires participants to recall a sequence of numbers in reverse order (maximum score: 9). The memory capacity evaluated with these two tasks is defined as the longest sequence that participants can repeat without errors, allowing two attempts for each sequence length (maximum score: 8).

Hair sample will be collected from the posterior vertex or nape area, where growth is continuous and less exposed to contaminants. For this, a small portion of hair will be tied with thread near the cut area, which will allow identification of the portion closest to the scalp at the time of analysis and prevent hair loss. Using clean scissors, the hair will be cut as close as possible to the scalp, obtaining a segment of approximately 3 cm in length. This will allow for the evaluation of cortisol levels accumulated over the last three months, as hair grows on average 1 cm per month.

Ad hoc questionnaire to assess:

Sex, age, place of residence, marital status, employment status, lifestyle habits (smoking, alcohol, physical activity, diet), vaccination against SARS-CoV-2 information.

This questionnaire is designed to assess the symptoms and impact of long COVID-19 symptoms on patients' daily lives. It evaluates information about physical and cognitive function as well as levels of fatigue and COVID-19 infection history.