Traditionally, in Europe, what has been understood as harmful to minors has been defined at Member State level with sensitivities toward social and cultural perspectives and state level regulation.  However, the question nowadays is whether or not these sorts of approaches are sustainable in a global cross media content environment.

Whilst it is presumed that harmful content inherently causes negative effects through exposure, a critically evaluative evidence base for this has been lacking due to the methodological difficulties fraught in this area.
A meta-analysis of the research to date suggests that it is useful to broadly divide harmful content into areas which affect physical, psychological, social and moral development, especially with regard to minors. This be conceptualised in terms of:

• Emotion: Experience of negative emotions such as fear, shock and lack of understanding of viewed content
• Attitude: Development of scripts and schemas which guide behaviour, desensitisation and disinhibition
• Ideology: Reinforcement, legitimisation and justification of attitudes and behaviours
• Behaviour: Modelling and repetition of viewed behaviours

Categorisation of harmful content is further complicated by the complex communicative functions associated with content and services utilised for communication, e.g. reinforcement and legitimisation of specific and extreme ideologies through websites and associated communities e.g. pro-suicide sites, extremist political and religious ideologies.

Whilst many areas are more easily defined as being unsuitable or harmful to all, factors such as age prevent blanket classifications which can applied to our understanding of harm. Recognition is further needed of how access to emerging technologies allows not only children and adults to be recipients of content but also producers.

Whilst for example publishing one’s personal details on the web or partaking in activities such as blogging are not harmful in themselves, they may place individuals at risk of harm from others accessing content with ill-intent. 

In order to establish a greater framework for defining this area, the Council for Europe under the auspices of the Group of Specialists on Human Rights in the Information Society (MM-S-IS) has commissioned research to be conducted by Rachel O'Connell, Cyberspace Research Unit, which aims to elaborate the meaning of harmful content in order to better understand it and, as a corollary, to raise awareness and facilitate action among States to combat it.