What are the differences between a literature search, a literature review, a systematic review and a meta-analysis? And why is a systematic review considered to be so good?

peer-reviewedIt takes time to recognise the differences between a literature search (LS), a literature review (LR), a systematic review (SR) and a meta-analysis (MA), especially as these terms are often used interchangeably by many authors. For example, a colleague said recently that she planned to do SR as part of her background for her post-graduate research thesis. She planned to have it completed within five days. After talking to her, it was clear that she did not understand the concept (or the workload!) involved in a SR. On the other hand, we all do so-called “quick and dirty” LSs every day! Those are the kind of search where you have a question, you open up your favourite search engine (PubMed, EMBASE, etc.), plug in a few key words and press “search”. Usually, with this type of search, you only put more effort into the search strategy if the “quick and dirty” approach does not yield enough (or any) relevant articles or if you are doing the LR for your thesis, or research project