A major depression prognosis calculator based on episode duration

Table 2 Estimated annual incidence and Weibull parameters for major depression

Year	N	Approximate incidence proportion*	Model-Based Estimates
			Approximate Incidence Proportion*	Adjusted Annual Incidence**	Weibull Scale Parameter	Weibull Shape Parameter
1994–96	9370	3.5%	3.5%	2.8%	52.9	0.66
1996–98	9689	3.6%	3.6%	2.8%	52.9	0.66
1998–00	9427	3.8%	3.8%	3.1%	47.4	0.71
2000–02	9244	3.8%	3.8%	3.1%	47.9	0.86

* proportion without an episode in the year preceding the start of the interval (1994, 1996, 1998 or 2000) who have an episode in the year preceding the following interview.
** using the exponential formula (2 year incidence = 1 - e^{-one year rate*2}) these annual rates correspond to predicted 2-year incidence ranging from 5.4% to 6.0%.