When I was an undergraduate student, and later a graduate student, if I wanted a summary of the state of the literature pertaining to a research question the narrative review was the primary - and in many cases - the only choice. For those needing a refresher, a narrative review is one in which the author or authors pick a set of studies to summarize, and then offer an intensive analysis of what that literature tells us about how well a particular research hypothesis is holding up. As someone who has certainly read my share of narrative reviews, and authored or coauthored a few of my own, such reviews do have a place. If done even remotely well, a narrative review can offer an encyclopedic summary of a research area, or a quick summary of recent research and theory for a particular line of inquiry.
The problem with narrative reviews was that they were ultimately subjective. Everything from the selection of articles to examine to the conclusions drawn was based ultimately on the particular whims of the authors. With such subjectivity, we were bound to find conflicting narrative summaries on any topic imaginable. If one had sufficient expertise in an area, one could quickly get to know the players well enough to suss out the perspective a particular author or team of authors would likely offer. If one were interested in whether or not psychotherapy was effective, for example, any literature review by Hans Eysenck was going to be predictably negative. However, for novices, or those simply wishing to reinforce pre-existing biases, narrative reviews were highly problematic.
Early narrative reviews on the weapons effect are particularly instructive. Depending on whether one read the work of Leonard Berkowitz and his former students or read the work of researchers who were downright skeptical to the point of cynicism, one would either be convinced that a weapons effect was real or that a weapons effect was non-existent. To make things even more frustrating, in the early 1990s, two book chapters in the same volume were published where competing authors examined mostly the same studies and came to radically different conclusions regarding the existence of the weapons effect. For any of us seeking some closer approximation of truth, such a situation was untenable.
The meta-analysis offered a promising alternative to that untenable set of circumstances. I will turn to that topic shortly.