Unspecific low back pain (LBP) is a major world wide health problem. The purpose of this study is to improve the care of LBP. Our hypothesis is that Cognitive Behavioural Therapy (CBT) with physical intervention during group sessions focusing on fear and avoidance behaviour will be more effective than physical therapy alone. The study has two arms. Both will receive education related to LBP and appropriate advice regarding how to react and behave towards their LBP. The main focus in the intervention group will be: * Identifying their fear of movements and perform the frightened movements during the group sessions. * Reassuring that gradually normalizing daily activities will not be harmful but rather reduce their pain.
Inclusion Criteria: * Low Back Pain (LBP) lasting from 3 months to 10 years. * Pain of such a severity that life of quality is reduced. * The patient's main problem must be LBP, localized from L1 to S1. * The pain must not be caused by nerve root affection (e.g. herniated disc) * The patient has to be able to understand instructions given in Norwegian and to take part in a group activity. * The patient must be partly or fully on sick leave from work. * The patient must have a regular work to return to. Exclusion Criteria: * 100 % disability pension, of any reason. * LBP that clearly is secondary to other somatic or psychiatric disorders. * Alcohol and drug abuse. * LBP caused by ankylosing spondylitis and other spondylarthropathies. * Patients with "red flags" such as bladder- and anal paresis, impotence or progressing paresis. * Ongoing insurance affairs for all types of sickness, injuries and accidents both against insurance companies and NAV (The Norwegian Labour and Welfare Administration) * Indication for back surgery or performed back surgery last 12 months * On medication known to cause depression or other psychiatric symptoms