| Value | Category | 
                                    
                    
                        | 1 | 1. Never | 
                                    
                    
                        | 2 | 2. >= 1* year | 
                                    
                    
                        | 3 | 3. >= 1* mnth | 
                                    
                    
                        | 4 | 4. >= 1* week | 
                                    
                    
                        | 5 | 5. Daily | 
                                    
                    
                        | 9 | 9. Miss | 
                                    
                    
                        | Sysmiss |  | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.