The target groups are adult (18 to 65 years) and elderly (over 65 years) patients with a Serious Mental Illness. Inclusion criteria: presence of SMI and behavioral problems, willingness and ability to participate in this research.

The first step is analysis of the behavioral problem because the core need is insufficiently compensated by the current environment or counteracted by the behavior of people within that environment. Step 2 is to choose the right core need based on this analysis. CoMBI-SMI describes the patient's self-image, the image of others, the triggering events and the problematic behavior of the patient based on personality disorders as classified by the Diagnostical and Statistical Manual of Mental Disorders. Step 3 is to choose the nursing intervention that is easily deployable so that Healthcare providers can identify the underlying core need and reduce the behavioral problems and burden on the healthcare providers. The fourth and final step is to draw up a CoMBI plan. The CoMBI-SMI is a cyclical process where it is important that the entire team is aligned with the patient's behavioral approach. Interventions are carried out by the entire team and evaluated after an agreed period of time.

The NPI-Q was developed and validated in 2000 and translated into Dutch in 2002. The NPI-Q contains 12 domains that can be used to map neuropsychiatric symptoms. These domains are: delusions; hallucinations; agitation/aggression; depression/dysphoria; fear; euphoria / elation; apathy/indifference; disinhibited behavior; irritability/lability; aimless repetitive behavior; night restlessness/sleep disorder; appetite/eating behavior change. The questionnaire is completed by the patient's caregiver and charts whether a particular symptom is present or not, how severe this symptom is (on a three-point scale) if present, and how severe the emotional burden of this symptom is for the caregiver (on a six-point scale). The test-retest correlation of the NPI-Q for symptom severity is 0.80 and for emotional burden is 0.94. The convergent validity, compared to the NPI, is 0.91 for symptom severity and 0.92 for emotional burden.

The Brief Symptom Inventory (BSI) is a multidimensional complaints list that shows the extent to which the patient suffered from psychological and/or physical symptoms during the past period. This test also gives a score for the total number of complaints, the total symptoms present and the severity of the symptoms present. The test consists of 53 items scored from "not at all = 0" to "very much = 4". There are 9 subscales: Somatic complaints; Cognitive problems; Interpersonal sensitivity; Depressed mood; Fear; Hostility; Phobic fear; Paranoid thoughts; Psychoticism. The test is sensitive to therapy influences. The BSI is a sufficiently reliable and valid test. The test is standardized for the Dutch language area with the norm groups men vs. women and general population vs. patients. The currently available norm groups were established in 2011.

The Mental Health Quality of Life (MHQoL-7D) measures the quality of life in people with mental health problems. The MHQoL-7D is a standardized instrument consisting of two parts: a descriptive section, the MHQoL-7D, and a visual analog scale. The MHQoL-7D consists of seven questions covering seven dimensions, each with four response levels ranging from very satisfied to very dissatisfied: self-esteem, independence, mood, relationships, daily activities, physical health, and future. The total score can range from 0 to 21; the higher the score, the better the quality of life. The MHQoL visual analog scale measures the respondent's general psychological well-being on a horizontal scale ranging from zero, 'only imaginable psychological well-being' to ten, 'best imaginable psychological well-being'.

The Personality Inventory for Diagnostic and Statistical Manual of Mental Disorders edition 5 is a 220-item self-report list of five domains (Negative Affectivity, Detachment, Antagonism, Disinhibition and Psychoticism) and the 25 associated facets of Criterion B measured from the Alternative Personality Disorder Model. The instrument can be used as a reliable screening measure for dimensional maladaptive personality traits. From the longer version PID-5-dutch version it is possible to use the shorter version, the PID-5-Brief form+Modified. The proposed study uses the shortened self-report version and informant version of the derived Dutch version, the PID-5-Brief form+Modified. This version consists of 36 self-report items (all part of the original PID-5) and covers a combination of the five Diagnostic and Statistical Manual of Mental disorders edition 5 domains and the Internation Classification of diseases edition 11 personality trait domain Anankastic, resulting in six domains.