NTT DoCoMo (the largest Japanese telecom company)'s customer service department recently tweeted an image purportedly showing the harmful effects of overusing smartphones:

enter image description here

To me, at least, the photo looks suspiciously doctored, and I was not aware of any reason why the relatively light weight of a smartphone can cause such a deformity.

The Google Translate of the tweet information:

[Finger is deformed! ? ] ... Also depending on how to hold the smartphone to become "text thumb injury". So that it is not too much a burden on a particular finger, but please take the time to time how to hold a change or break.

Native Japanese speakers are welcome to suggest edits and/or provide a proper translation, but it seems quite clear (to a Chinese speaker) that they are suggesting that the finger deformity is caused by holding the smartphone.

The belief of "smartphone pinky" being a real phenomenon is also corroborated by Rocket News 24 (an English blog about Japan) which cites the above Twitter post, as well as Urban Dictionary, which attests that the deformation is permanent.

  • 4
    You made me look at my pinkies, and they look a lot like the photo
    – Evorlor
    Mar 11, 2015 at 1:38
  • 6
    @Evorlor Both of mine look at least similar to that (at the right angle). This is despite holding my phone left-handed far more than right-handed.
    – Is Begot
    Mar 11, 2015 at 13:37
  • 1
    Mine look somewhat similar too, and I've never owned or used a smartphone.
    – jamesqf
    Mar 11, 2015 at 19:01
  • 2
    Found an article on nlab.itmedia (from 2015, 10th of March) saying text thumb injury (テクスサム症) originally referred to an inflammation of a tendon sheath; and that the confusion with a deformation of your finger resulted from a misunderstanding of an article from jcast. The article also claims that they made an inquiry to docomo, who stated that the tweet wasn't based upon medical evidence but because many people were reporting it on net
    – blutorange
    Mar 12, 2015 at 23:36
  • 1
    Snopes has addressed it: snopes.com/politics/medical/smartphonepinky.asp Mar 16, 2015 at 21:06

1 Answer 1


Short answer, no. It is possible to sustain Repetitive Stress Injuries (RSI) from smartphone usage, much like the early traumas of "Blackberry Thumb" and "Nintendonitis", but these will not create permanent deformity of the fingers. As covered in the Snopes article on the phenomenon, the most likely explanation for people posting pictures of their ostensible damage is clinodactyly, a common slight curvature of the fingers caused by genetics which most people are unaware that they have until they look.


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