Yes, back pain is often caused by unconscious emotional issues. Such pain is called psychosomatic or psychogenic pain; common associated terms include myofascial pain, tension myositis, fibromyalgia and central sensitization.
1) Sarno JE, Psychosomatic backache (The Journal of Family Practice, 1977):
It is contended in this report that the majority of pain syndromes
involving the neck, shoulders, and low back are the result of a
benign, reversible process in the musculature which is psychosomatic
in nature and which has been called tension myositis.
2) Work strain and symptoms of musculoskeletal disorders (The National Institute for Occupational Safety and Health, 1999):
Elevated state anxiety was directly related to symptoms, while
depression and psychosomatic symptoms acted as mediators between job
and home demands and MSD symptoms, especially symptoms in the lower
3) Central sensitization in chronic low back pain: A narrative review (Journal of Back and Musculoskeletal Rehabilitation, 2016):
The etiology of chronic low back pain is, in most of the cases (up to
85%), unknown or nonspecific, while the specific causes (specific
spinal pathology and neuropathic/radicular disorders) are uncommon.
Central sensitization has been recently recognized as a potential
pathophysiological mechanism underlying a group of chronic pain
conditions, and may be a contributory factor for a sub-group of
patients with chronic low back pain.
4) The Psychology of Pain (Emergency Medical Clinics of North America, 2005):
The National Institutes of Health Technology Assessment Conference
Statement... identified six factors that correlated with treatment
failures of low back pain—all were psychosocial. Even chronic,
episodic, low back pain may have a vital component of socioeconomic
and psychological influences.
Regarding treatment: Psychosomatic pain arises from personal issues and resolving them can resolve the pain. It's a person with pain who needs to solve personal problems, which can include false believes, wrong attitudes, bad relationships, inappropriate job, etc. Regular discussion with an emphatic and experienced person can help but relying on various therapeutic "techniques" can be disappointing.