AC	Main Active Component used in the intervention
ACT	Acceptance and Commitment Therapy
AT	Art Therapy
CBT	Cognitive Behavioral Therapy
CI	Confidence Interval
CG	Control Group
Coll	Collectivistic
DA	Delayed Access
DJLS	de Jong–Gierveld Loneliness scale
D-SS	Digital Social Support
I-C	Intervention vs. Control
I-I	Intervention vs. Intervention
Ind	Individualistic
INSPECT-SR	INveStigating ProblEmatic Clinical Trials in Systematic Reviews
IPT	Internet-Based Interpersonal Therapy
MM	Mindful Movement
Medt	Meditation
NHS	National Health System
NI	No Intervention
NNT	Number Needed to Treat
N-On	Non-online Interaction Group
N/r	Number of sessions not reported
n/r	Length or age not reported
OD	Online Diary
OSF	Open Science Framework
PA	Physical Activity
PRISMA	Preferred Reporting Items for Systematic Reviews and Meta-Analyses
RCT	Randomized Controlled Trial
RoB	Risk of Bias
SS	Social Support
SMD	Standardized Mean Differences
UCLA (v3)	University of Los Angeles Loneliness scale (version three)
UK	United Kingdom
VI	Virtual Interaction with Strangers
WL	Waiting List
WHO	World Health Organization
YT-i	YouTube interaction