Emerging research has shown that social media services are being used as tools to disclose a range of personal health information. To explore the role of social media in the discussion of mental health issues, and with particular reference to insomnia and sleep disorders, a corpus of 18,901 messages - or Tweets - posted to the microblogging social media service Twitter were analysed using a mixed methods approach. We present a content analysis which revealed that Tweets that contained the word “insomnia” contained significantly more negative health information than a random sample, strongly suggesting that individuals were making disclosures about their sleep disorder. A subsequent thematic analysis then revealed two themes: coping with insomnia, and describing the experience of insomnia. We discuss these themes as well as the implications of our research for those in the interaction design community interested in integrating online social media systems in health interventions.