Up till now, post-awakening bright light therapy has been tested most extensively in clinical trials and received professional task force endorsement by the Society for Light Treatment and Biological Rhythms and the American Psychiatric Association, among others. It is quite possible that ionization and dawn simulation will be shown equally effective as bright light, but these are newer developments and the data base for them is smaller. Conservatively, we advise new patients to start with bright light therapy, and then move to (or add) the other methods as follow-up options. Yes, a given patient may respond to one, but not another, of these treatments. Presumably, bright light therapy and dawn simulation act by the same mechanism, and ultimately the choice between them may be based on convenience.