Wittouck
et al. (2011) conducted a meta-analysis to evaluate the short-term and
long-term effect of grief prevention as well as treatment on individuals with
complicated grief. They used two methods to gather articles they needed. The
first includes the electronic databases Web of Science (WOS) and PsycArticles,
the second method is utilizing the relevant studies from the reference list.

The inclusion criteria are listed as following: 1) the study conducted Randomized
Controlled Trial (RCT) and included a comparison group, 2) the participants of
the intervention were adults who lost their significant others, 3) the
assessments included pre-and post or follow-up evaluation, 4) the outcome
variable involved the complicated grief, 5) the study was published in peer-reviewed
journal, 6) the published year of the study was from 1990 to 2007. They
excluded case studies, treatments for diagnoses relevant to other loss, treatments
for children, teenagers, caregivers, people with intellectual disabilities or people
with pet loss, treatments for people with life-limiting diseases, and drug
therapy.