In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: CONCLUSIONS : The increases in anxiety and depression are in line with previous observations in recreational ecstasy - polydrug users .
### Output Text:
CONCLUSIONS : The increases in anxiety and depression are in line with previous observations in recreational <span class="chemical">ecstasy</span> - polydrug users . 