Purpose
This systematic review aimed to assess (1) the level of comorbidity of post-traumatic stress disorder (PTSD) and alcohol misuse reported in research studies since 2007 and (2) any associations found between specific PTSD symptom clusters and alcohol misuse.

Methods
A literature search was carried out to capture any papers published from 2007 to the end of July 2012. Six hundred and twenty abstracts were identified and reviewed, and 42 papers were included in the final review after applying inclusion and exclusion criteria.

Results
The prevalence of comorbid alcohol misuse in those with PTSD ranged from 9.8 to 61.3 %. The prevalence of comorbid PTSD in those with alcohol misuse ranged from 2.0 to 63.0 %, and the majority of prevalence rates were over 10.0 %. Almost all of the odds ratios representing the strength of association between the conditions across a variety of populations were significant, and those ranged from 1.1 to 4.87. Of the different PTSD symptom clusters, this review found most evidence for associations between alcohol misuse and both avoidance/numbing symptoms and hyperarousal symptoms.

Conclusions
Given that comorbidity appears to be common, the evidence from this systematic review supports the use of routine screening for comorbidity in populations who are known to have PTSD or alcohol misuse.