TABLE 5.

Clusters of co-occurring keywords.

Cluster	Size	Silhouette	Mean year	Label (LLR algorithm)
0	75	0.661	2015	Magnetic resonance spectroscopy
1	73	0.761	2014	Propofol
2	73	0.805	2015	Hippocampus
3	60	0.760	2014	Electroconvulsive therapy
4	59	0.810	2014	Transcranial magnetic stimulation
5	43	0.748	2016	Machine learning
6	43	0.814	2016	Bipolar disorder
7	42	0.789	2014	Dementia
8	33	0.804	2016	Attitude