[achikin]

https://pmc.ncbi.nlm.nih.gov/articles/PMC6174603/

The main idea here is that overuse not equals addiction.

[justinclift]

The first part of the Results section says:

    [...] the majority of research in the field declares that smartphones are addictive

Though that section continues on to disagree with that majority, "the majority" declaring smartphones are addictive is certainly supportive of them being so.