There are many reasons why someone might take selfies. Equally valid reasons include: (a) you're a girl and you just spent hours on awesome makeup that you now want to keep record of, (b) it's fun, or (c) you're bored.
The kind of science that misinterprets a simple, valid correlation between two factors (in this case selfies and various psychological disorders) as confirmed evidence of clinical psychosis or narcissistic personality disorder or insecurity in those that partake in the activity under study is quite simply very bad science.