What is an indirect association?

Indirect associations between targets and diseases are computed based on indirect evidence, rather than observed (direct) evidence.

If you search for a target using the web interface of the Open Targets Platform, you will get associations based on direct evidence only. However, if you search for a disease, you will get both direct and indirect associations, since we propagate evidence from lower sections of a disease ontology, this evidence is used as indirect evidence for the associations.

When retrieving our data via the Open Targets REST API, you will get two types of association counts:

Association counts when searching for Alzheirmer's using the REST API search endpoint

The difference betweentotalanddirectis the number of associations based on indirect evidence.

To get direct associations only, you should include the parameter direct = true when using our REST-API endpoints, such as the association/filter below:


We propagate the indirect evidence from a child term up to its parent term in the disease ontology for all diseases in our Platform. By computing new target-disease associations when there is no direct (known and observed) evidence for them, we allow:

  • finding common targets across groups of related diseases (e.g. ulcerative colitis, Crohn's disease and inflammatory bowel disease)

  • making connections between rare and common diseases (e.g. autosomal recessive early-onset inflammatory bowel disease and inflammatory bowel disease)

  • grouping evidence for all diseases within a therapeutic area

  • identifying unforeseen associations by serendipity

Read our Direct versus indirect evidence: should you care? blog post for more details and email us if you have further questions.