The MOST important factor in evaluating the credibility of the article "Social Media: Friend or Foe?" would be the author's qualifications and expertise in psychology.
An author's qualifications and expertise are crucial in determining the reliability and validity of the claims made in the article. If the author has a strong background in psychology, mental health, or a related field, they are more likely to provide a well-informed analysis of the impact of social media on mental health.