| Cover | Aug. 31, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 31, 2020 |
| Entity File Number | 001-37635 |
| Entity Registrant Name | Axsome Therapeutics, Inc. |
| Entity Central Index Key | 0001579428 |
| Entity Tax Identification Number | 45-4241907 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 22 Cortlandt Street |
| Entity Address, Address Line Two | 16th Floor |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10007 |
| City Area Code | 212 |
| Local Phone Number | 332-3241 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, Par Value $0.0001 Per Share |
| Trading Symbol | AXSM |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | true |
