Medical treatment, or behavioral therapy or a coordination of behavioral therapy and medical treatment. Meeting with a rehabilitation coordinator.

Change from baseline in return to work during a follow-up of 18 months. Return to work will be calculated from baseline data until the individual returns to work in ordinary hours during an uninterrupted period of at least four weeks.

Episodes of sick leave after full-time return to work (i.e. work in ordinary hours during an uninterrupted period of at least four weeks) will be calculated from baseline until the 18 months follow-up by registered sickness absenteeism.

Change in total registered sickness absenteeism at baseline and during the 36 months follow-up (including sickness benefit, sickness and activity compensation, disability pension). Data from the Social Insurance Agency's register MiDAS.

Possible interaction effects on the primary and secondary outcomes for (1) gender x treatment, and (2) number of sessions with rehabilitation coordinator x treatment will be checked for and if statistically significant subgroup analyses will be considered.

Change in self-reported sickness absenteeism from baseline during the 12 month follow-up. Self-reported data collected every fourth week during the 12 months. These self-reported data cover shorter spells of sickness absenteeism (i.e. ≤14 consecutive days) that is not covered by the Social Insurance Agency's register.

Change from baseline in self-reported partial sickness absenteeism (25/50/75% of full-time sickness absenteeism) during a follow-up period of 12 months. Change in self-reported sickness absenteeism will be calculated from baseline until the 12 months follow-up in number of days on part-time sick leave (25/50/75% of full-time sick leave).

Change from baseline in self-reported return to work during a follow-up of 12 months. Return to work will be calculated from baseline data until the individual returns to work in ordinary hours during an uninterrupted period of at least four weeks. Self-reported data obtained every fourth week during a period of 12 months.

Episodes of self-reported sickness absenteeism after full-time return to work (i.e. work in ordinary hours during an uninterrupted period of at least four weeks) will be calculated from baseline until the 12 months follow-up by self-reported sickness absenteeism.

Hospital Anxiety and Depression Scale will be used to assess symptoms of anxiety (seven items) and depression (seven items). Each item is scored on a 4-point Likert scale indicating the extent to which an item was experienced in the past week. Response format from 0 to 3.

Institute of Stress Medicine's instrument for self-reported exhaustion: Change from baseline in self-reported exhaustion as measured by the Institute of Stress Medicine's instrument. Three items with the response format yes/no and one item with response format from 0 to 2.

Karolinska Sleep Questionnaire, Insomnia subscale will be used for assessing insomnia problems. The subscale includes four items. Each item is scored on a 6 point scale ranging from 0 (never) to 5 (always) indicating to what extent an item was experienced in the last three months. Change from baseline in self-reported sleep problems.

Sickness presenteeism will be measured with a single question, response format 1-4.

WAI: change from baseline and after 6 and 12 months after study inclusion, self-reported work ability is assessed by 2 items from WAI (with the response format 1 - 5). These questions measures the perceived work capacity in relation to the physical (1 item) and the mental (1 item) demands of the work.

Work performance due to health problems will be measured by a question from one of the items included in the Work Productivity Impairment - General Health Questionnaire (the response format is 0-10).

Work performance due to problems in the working environment will be measured by a question from one of the items included in the Work Productivity Impairment - General Health Questionnaire (the response format is 0-10).

Demand-control-support model: Change from baseline and after 6 and 12 months after study inclusion, response format from 1 to 4. Prognostic variable.

Return-to-work self-efficacy will be measured by a question with the response format from 0 to 10. Prognostic variable.

Ongoing conflict with the superior is measured by one item. The item is scored on a 3 point Likert-type scale ranging from 0 (never) to 3 (often or always). Prognostic variable.

Perceived loss of control over work tasks is measured by one item. The item is scored on a Likert-type scales with 5 response options ranging from 0 (never or almost never) to 4 (very often or always). Prognostic variable.

Conflict between employee's values and how the work actually is done is measured by three items. Each item is scored on a Likert-type scale5 response options ranging from 0 (never or almost never) to 4 (very often or always). Prognostic variable.

Job strain (emotional and psychological demands) will be assessed by four items from Copenhagen psychosocial questionnaire, response format is likert-type scales with 5 response options. Prognostic variable.

Participants' satisfaction and experiences with their participation in the intervention or care as usual will be assessed at 6 months after completed intervention, as a part of the process evaluation. Self-reported questionnaire with ten items, response format from 0 to 10 or yes/no/do not know.

The rehabilitation coordinators' adherence to the intervention is measured by a single item with the response format from 1 to 5.

Health related quality of life will be measured with European Quality of Life 5 Dimensions questionnaire (EQ5D). The response format is a 3-level scale, with higher levels indicating severity.