The purpose of this research study is to study four treatments for chronic low-back pain to learn whether or not certain treatments work better for people with certain characteristics.The study's main goal is to find a way to match treatments to low-back pain patients based on their characteristics and how they responded to treatments they have used before.

This study is a multi-site, sequential, multiple assignment randomized trial (SMART) designed to meet the primary objective of estimating an algorithm for optimally assigning evidence-based interventions for chronic low-back pain. The trial is based on an individual patient's phenotypic markers and response to treatment. Interventions being evaluated in this trial are: (1) acceptance and commitment therapy (ACT), (2) duloxetine, (3) enhanced self-care (ESC), and (4) evidence-based exercise and manual therapy (EBEM).