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Table 1 Interpretation of probabilities estimated from each multi-state structure

From: Exploring different research questions via complex multi-state models when using registry-based repeated prescriptions of antidepressants in women with breast cancer and a matched population comparison group

Multi-state structure

Research questions answered in terms of probabilities

Single-event survival analysis of time to antidepressant medication initiation (Fig. 1A)

What is the probability of ever been prescribed medication in the hypothetical situation that the individual cannot die due to any causes?

Competing risks for time to medication initiation with death as a competing event (Fig. 1B)

What is the probability of ever been prescribed medication up to time \(t\) after the start of the follow-up, accounting for the fact that individuals may die?

3-state Illness-Death model adding a transition from medication initiation to death (Fig. 1C)

What is the probability of ever been prescribed medication and still be alive up to time \(t\) after the start of the follow-up?

4-state unidirectional multi-state model with a medication discontinuation state (Fig. 1D)

What is the probability of being in the 1st medication cycle since start of follow up/ since entering the 1st medication cycle?

4-state Bidirectional multi-state structure with medication discontinuation state (Fig. 1E)

What is the probability of being in a medication cycle (or in a medication discontinuation period) since the start of follow-up or given entering one?

Recurrent events multi-state structure (with or w/o restrictions)

(Fig. 1F and G)

• What is the total probability of being in a medication cycle since the start of follow-up or given entering the 1st, 2nd, 3rd one?

• What is probability of being in the current medication cycle given entering the 1st, 2nd, 3rd medication cycle or the 1st, 2nd, 3rd discontinuation period?

  1. The list above is not an exhaustive list of multi-state structures that can be used and research questions that can be addressed. The estimated measures can be compared between the exposure groups of interest. We highlight in bold the subtle differences in phrasing the research questions when interpreting the probabilities of multi-state structures D, E, F and G (1st,a, the current medication cycle)