-I am trying to figure out whether the method used in this article is considered experimental, nonexperimental, or quasiexperimental strategy? (I posted the methods only part of the article)

-I believe that it is nonexperimental, as the researcher used other researched articles to come to the conclusion. Please help!

Methods

Recent and relevant publications were located using the keywords "ADHD" and "sleep" with PubMed, Google Scholar and PsycINFO. Selected articles included quantitative research published since 2012 that examined any aspect of childhood ADHD and sleep and excluded redundant case studies. Reviews were also excluded from the primary search. The selected articles and methodologies are displayed in Table1.

Table1Selected articles and methodologies