In recent years, a "myth" of sorts has sprung up, where people who avoid animal foods believe they can simply consume plant-based omega-3 ALA to meet their needs. But this isn't true and the science doesn't support this assertion.
Omega-3s EPA and DHA from marine animal and plant sources are NOT interchangeable.
Plant sources that contain omega-3 ALA do not provide the same benefits as the omega-3s you find in marine sources.
Omega-3 from fish is especially important post addiction, because we basically de-fat" our brain and nerves, when we take drugs, alcohol and even many eating disorders also tend to result in this.
Omega-3 is clinically shown to provide a lowered risk for neurological/cognitive dysfunction, including: memory loss, brain aging, learning disorders and ADHD and autism.
Although our body can convert some of the ALA found in plants to the DHA found in marine oils, it is very rare for it to be more than 5 percent and typically found to be 1 to 3 percent, or even less. This is an insufficient amount to have any significant benefit.
Reference: Omega-3 Institute, Differentiation of ALA (plant sources) from DHA + EPA (marine sources) as Dietary Omega-3 Fatty Acids for Human Health.